Top 100 JavaScript Snippets for Beginners
When developing a program in JavaScript (or any language, for that matter) you will often find yourself choosing between DIY code and existing code snippets to do what you need. Being able to find the snippet you need when you need it can save you a lot of time and prevent those JavaScript writing headaches.
If this sounds compelling to you, here’s a list of 100 beneficial snippets taken from this project that you can learn and use immediately.
1. all
This snippet returns true if the predicate function returns true for all elements in a collection and false otherwise. You can omit the second argument fnif you want to use Booleanas a default value.
const all = (arr, fn = Boolean) => arr.every(fn);
all([4, 2, 3], x => x > 1); // true
all([1, 2, 3]); // true
2. allEqual
This snippet checks whether all elements of the array are equal.
const allEqual = arr => arr.every(val => val === arr[0]);
allEqual([1, 2, 3, 4, 5, 6]); // false
allEqual([1, 1, 1, 1]); // true
3. approximatelyEqual
This snippet checks whether two numbers are approximately equal to each other, with a small difference.
const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
approximatelyEqual(Math.PI / 2.0, 1.5708); // true
4. arrayToCSV
This snippet converts the elements that don’t have commas or double quotes to strings with comma-separated values.
const arrayToCSV = (arr, delimiter = ',') =>
arr.map(v => v.map(x => `"${x}"`).join(delimiter)).join('\n');
arrayToCSV([['a', 'b'], ['c', 'd']]); // '"a","b"\n"c","d"'
arrayToCSV([['a', 'b'], ['c', 'd']], ';'); // '"a";"b"\n"c";"d"'
5. arrayToHtmlList
This snippet converts the elements of an array into `` tags and appends them to the list of the given ID.
const arrayToHtmlList = (arr, listID) =>
(el => (
(el = document.querySelector('#' + listID)),
(el.innerHTML += arr.map(item => `<li>${item}</li>`).join(''))
))();
arrayToHtmlList(['item 1', 'item 2'], 'myListID');
6. attempt
This snippet executes a function, returning either the result or the caught error object.
const attempt = (fn, ...args) => {
try {
return fn(...args);
} catch (e) {
return e instanceof Error ? e : new Error(e);
}
};
var elements = attempt(function(selector) {
return document.querySelectorAll(selector);
}, '>_>');
if (elements instanceof Error) elements = []; // elements = []
7. average
This snippet returns the average of two or more numerical values.
const average = (...nums) => nums.reduce((acc, val) => acc + val, 0) / nums.length;
average(...[1, 2, 3]); // 2
average(1, 2, 3); // 2
8. averageBy
This snippet returns the average of an array after initially doing the mapping of each element to a value using a given function.
const averageBy = (arr, fn) =>
arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0) /
arr.length;
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5
9. bifurcate
This snippet splits values into two groups and then puts a truthy element of filterin the first group, and in the second group otherwise.
You can use Array.prototype.reduce()and Array.prototype.push()to add elements to groups based on filter.
const bifurcate = (arr, filter) =>
arr.reduce((acc, val, i) => (acc[filter[i] ? 0 : 1].push(val), acc), [[], []]);
bifurcate(['beep', 'boop', 'foo', 'bar'], [true, true, false, true]);
// [ ['beep', 'boop', 'bar'], ['foo'] ]
10. bifurcateBy
This snippet splits values into two groups, based on a predicate function. If the predicate function returns a truthy value, the element will be placed in the first group. Otherwise, it will be placed in the second group.
You can use Array.prototype.reduce()and Array.prototype.push()to add elements to groups, based on the value returned by fnfor each element.
const bifurcateBy = (arr, fn) =>
arr.reduce((acc, val, i) => (acc[fn(val, i) ? 0 : 1].push(val), acc), [[], []]);
bifurcateBy(['beep', 'boop', 'foo', 'bar'], x => x[0] === 'b');
// [ ['beep', 'boop', 'bar'], ['foo'] ]
11. bottomVisible
This snippet checks whether the bottom of a page is visible.
const bottomVisible = () =>
document.documentElement.clientHeight + window.scrollY >=
(document.documentElement.scrollHeight || document.documentElement.clientHeight);
bottomVisible(); // true
12. byteSize
This snippet returns the length of a string in bytes.
const byteSize = str => new Blob([str]).size;
byteSize('😀'); // 4
byteSize('Hello World'); // 11
13. capitalize
This snippet capitalizes the first letter of a string.
const capitalize = ([first, ...rest]) =>
first.toUpperCase() + rest.join('');
capitalize('fooBar'); // 'FooBar'
capitalize('fooBar', true); // 'FooBar'
14. capitalizeEveryWord
This snippet capitalizes the first letter of every word in a given string.
const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
capitalizeEveryWord('hello world!'); // 'Hello World!'
15. castArray
This snippet converts a non-array value into array.
const castArray = val => (Array.isArray(val) ? val : [val]);
castArray('foo'); // ['foo']
castArray([1]); // [1]
16. compact
This snippet removes false values from an array.
const compact = arr => arr.filter(Boolean);
compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34]);
// [ 1, 2, 3, 'a', 's', 34 ]
17. countOccurrences
This snippet counts the occurrences of a value in an array.
const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3
18. Create Directory
This snippet uses existsSync() to check whether a directory exists and then mkdirSync() to create it if it doesn’t.
const fs = require('fs');
const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);
createDirIfNotExists('test');
// creates the directory 'test', if it doesn't exist
19. currentURL
This snippet returns the current URL.
const currentURL = () => window.location.href;
currentURL(); // 'https://medium.com/@fatosmorina'
20. dayOfYear
This snippet gets the day of the year from a Dateobject.
const dayOfYear = date =>
Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);
dayOfYear(new Date()); // 272
21. decapitalize
This snippet turns the first letter of a string into lowercase.
const decapitalize = ([first, ...rest]) =>
first.toLowerCase() + rest.join('')
decapitalize('FooBar'); // 'fooBar'
decapitalize('FooBar'); // 'fooBar
22. deepFlatten
This snippet flattens an array recursively.
const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));
deepFlatten([1, [2], [[3], 4], 5]); // [1,2,3,4,5]
23. default
This snippet assigns default values for all properties in an object that are undefined.
const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 }
24. defer
This snippet delays the execution of a function until the current call stack is cleared.
const defer = (fn, ...args) => setTimeout(fn, 1, ...args);
defer(console.log, 'a'), console.log('b'); // logs 'b' then 'a'
25. degreesToRads
This code snippet can be used to convert a value from degrees to radians.
const degreesToRads = deg => (deg * Math.PI) / 180.0;
degreesToRads(90.0); // ~1.5708
26. difference
This snippet finds the difference between two arrays.
const difference = (a, b) => {
const s = new Set(b);
return a.filter(x => !s.has(x));
};
difference([1, 2, 3], [1, 2, 4]); // [3]
27. differenceBy
This method returns the difference between two arrays, after applying a given function to each element of both lists.
const differenceBy = (a, b, fn) => {
const s = new Set(b.map(fn));
return a.filter(x => !s.has(fn(x)));
};
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]
28. differenceWith
This snippet removes the values for which the comparator function returns false.
const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b));
// [1, 1.2]
29. digitize
This snippet gets a number as input and returns an array of its digits.
const digitize = n => [...`${n}`].map(i => parseInt(i));
digitize(431); // [4, 3, 1]
30. distance
This snippet returns the distance between two points by calculating the Euclidean distance.
const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
distance(1, 1, 2, 3); // 2.23606797749979
31. Drop Elements
This snippet returns a new array with n elements removed from the left.
const drop = (arr, n = 1) => arr.slice(n);
drop([1, 2, 3]); // [2,3]
drop([1, 2, 3], 2); // [3]
drop([1, 2, 3], 42); // []
32. dropRight
This snippet returns a new array with n elements removed from the right.
const dropRight = (arr, n = 1) => arr.slice(0, -n);
dropRight([1, 2, 3]); // [1,2]
dropRight([1, 2, 3], 2); // [1]
dropRight([1, 2, 3], 42); // []
33. dropRightWhile
This snippet removes elements from the right side of an array until the passed function returns true.
const dropRightWhile = (arr, func) => {
while (arr.length > 0 && !func(arr[arr.length - 1])) arr = arr.slice(0, -1);
return arr;
};
dropRightWhile([1, 2, 3, 4], n => n < 3); // [1, 2]
34. dropWhile
This snippet removes elements from an array until the passed function returns true.
const dropWhile = (arr, func) => {
while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);
return arr;
};
dropWhile([1, 2, 3, 4], n => n >= 3); // [3,4]
35. elementContains
This snippet checks whether the parent element contains the child.
const elementContains = (parent, child) => parent !== child && parent.contains(child);
elementContains(document.querySelector('head'), document.querySelector('title')); // true
elementContains(document.querySelector('body'), document.querySelector('body')); // false
36. Filter Duplicate Elements
This snippet removes duplicate values in an array.
const filterNonUnique = arr => [ …new Set(arr)];
filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 2, 3, 4, 5]
37. findKey
This snippet returns the first key that satisfies a given function.
const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
findKey(
{
barney: { age: 36, active: true },
fred: { age: 40, active: false },
pebbles: { age: 1, active: true }
},
o => o['active']
); // 'barney'
38. findLast
This snippet returns the last element for which a given function returns a truthy value.
const findLast = (arr, fn) => arr.filter(fn).pop();
findLast([1, 2, 3, 4], n => n % 2 === 1); // 3
39. flatten
This snippet flattens an array up to a specified depth using recursion.
const flatten = (arr, depth = 1) =>
arr.reduce((a, v) => a.concat(depth > 1 && Array.isArray(v) ? flatten(v, depth - 1) : v), []);
flatten([1, [2], 3, 4]); // [1, 2, 3, 4]
flatten([1, [2, [3, [4, 5], 6], 7], 8], 2); // [1, 2, 3, [4, 5], 6, 7, 8]
40. forEachRight
This snippet executes a function for each element of an array starting from the array’s last element.
const forEachRight = (arr, callback) =>
arr
.slice(0)
.reverse()
.forEach(callback);
forEachRight([1, 2, 3, 4], val => console.log(val)); // '4', '3', '2', '1'
41. forOwn
This snippet iterates on each property of an object and iterates a callback for each one respectively.
const forOwn = (obj, fn) => Object.keys(obj).forEach(key => fn(obj[key], key, obj));
forOwn({ foo: 'bar', a: 1 }, v => console.log(v)); // 'bar', 1
42. functionName
This snippet prints the name of a function into the console.
const functionName = fn => (console.debug(fn.name), fn);
functionName(Math.max); // max (logged in debug channel of console)
43. Get Time From Date
This snippet can be used to get the time from a Dateobject as a string.
const getColonTimeFromDate = date => date.toTimeString().slice(0, 8);
getColonTimeFromDate(new Date()); // "08:38:00"
44. Get Days Between Dates
This snippet can be used to find the difference in days between two dates.
const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
(dateFinal - dateInitial) / (1000 * 3600 * 24);
getDaysDiffBetweenDates(new Date('2019-01-13'), new Date('2019-01-15')); // 2
45. getStyle
This snippet can be used to get the value of a CSS rule for a particular element.
const getStyle = (el, ruleName) => getComputedStyle(el)[ruleName];
getStyle(document.querySelector('p'), 'font-size'); // '16px'
46. getType
This snippet can be used to get the type of a value.
const getType = v =>
v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase();
getType(new Set([1, 2, 3])); // 'set'
47. hasClass
This snippet checks whether an element has a particular class.
const hasClass = (el, className) => el.classList.contains(className);
hasClass(document.querySelector('p.special'), 'special'); // true
48. head
This snippet returns the head of a list.
const head = arr => arr[0];
head([1, 2, 3]); // 1
49. hide
This snippet can be used to hide all elements specified.
const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));
hide(document.querySelectorAll('img')); // Hides all <img> elements on the page
50. httpsRedirect
This snippet can be used to redirect from HTTP to HTTPS in a particular domain.
const httpsRedirect = () => {
if (location.protocol !== 'https:') location.replace('https://' + location.href.split('//')[1]);
};
httpsRedirect(); // If you are on http://mydomain.com, you are redirected to https://mydomain.com
51. indexOfAll
This snippet can be used to get all indexes of a value in an array, which returns an empty array, in case this value is not included in it.
const indexOfAll = (arr, val) => arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);
indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0,3]
indexOfAll([1, 2, 3], 4); // []
52. initial
This snippet returns all elements of an array except the last one.
const initial = arr => arr.slice(0, -1);
initial([1, 2, 3]); // [1,2]const initial = arr => arr.slice(0, -1);
initial([1, 2, 3]); // [1,2]
53. insertAfter
This snippet can be used to insert an HTML string after the end of a particular element.
const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);
insertAfter(document.getElementById('myId'), '<p>after</p>'); // <div id="myId">...</div> <p>after</p>
54. insertBefore
This snippet can be used to insert an HTML string before a particular element.
const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);
insertBefore(document.getElementById('myId'), '<p>before</p>'); // <p>before</p> <div id="myId">...</div>
55. intersection
This snippet can be used to get an array with elements that are included in two other arrays.
const intersection = (a, b) => {
const s = new Set(b);
return a.filter(x => s.has(x));
};
intersection([1, 2, 3], [4, 3, 2]); // [2, 3]
56. intersectionBy
This snippet can be used to return a list of elements that exist in both arrays, after a particular function has been executed to each element of both arrays.
const intersectionBy = (a, b, fn) => {
const s = new Set(b.map(fn));
return a.filter(x => s.has(fn(x)));
};
intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]
57. intersectionWith
This snippet can be used to return a list of elements that exist in both arrays by using a comparator function.
const intersectionWith = (a, b, comp) => a.filter(x => b.findIndex(y => comp(x, y)) !== -1);
intersectionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1.5, 3, 0]
58. is
This snippet can be used to check if a value is of a particular type.
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
is(Array, [1]); // true
is(ArrayBuffer, new ArrayBuffer()); // true
is(Map, new Map()); // true
is(RegExp, /./g); // true
is(Set, new Set()); // true
is(WeakMap, new WeakMap()); // true
is(WeakSet, new WeakSet()); // true
is(String, ''); // true
is(String, new String('')); // true
is(Number, 1); // true
is(Number, new Number(1)); // true
is(Boolean, true); // true
is(Boolean, new Boolean(true)); // true
59. isAfterDate
This snippet can be used to check whether a date is after another date.
const isAfterDate = (dateA, dateB) => dateA > dateB;
isAfterDate(new Date(2010, 10, 21), new Date(2010, 10, 20)); // true
60. isAnagram
This snippet can be used to check whether a particular string is an anagram with another string.
const isAnagram = (str1, str2) => {
const normalize = str =>
str
.toLowerCase()
.replace(/[^a-z0-9]/gi, '')
.split('')
.sort()
.join('');
return normalize(str1) === normalize(str2);
};
isAnagram('iceman', 'cinema'); // true
61. isArrayLike
This snippet can be used to check if a provided argument is iterable like an array.
const isArrayLike = obj => obj != null && typeof obj[Symbol.iterator] === 'function';
isArrayLike(document.querySelectorAll('.className')); // true
isArrayLike('abc'); // true
isArrayLike(null); // false
62. isBeforeDate
This snippet can be used to check whether a date is before another date.
const isBeforeDate = (dateA, dateB) => dateA < dateB;
isBeforeDate(new Date(2010, 10, 20), new Date(2010, 10, 21)); // true
63. isBoolean
This snippet can be used to check whether an argument is a boolean.
const isBoolean = val => typeof val === 'boolean';
isBoolean(null); // false
isBoolean(false); // true
64. isBrowser
This snippet can be used to determine whether the current runtime environment is a browser. This is helpful for avoiding errors when running front-end modules on the server (Node).
const isBrowser = () => ![typeof window, typeof document].includes('undefined');
isBrowser(); // true (browser)
isBrowser(); // false (Node)
65. isBrowserTabFocused
This snippet can be used to determine whether the browser tab is focused.
const isBrowserTabFocused = () => !document.hidden;
isBrowserTabFocused(); // true
66. isLowerCase
This snippet can be used to determine whether a string is lower case.
const isLowerCase = str => str === str.toLowerCase();
isLowerCase('abc'); // true
isLowerCase('a3@$'); // true
isLowerCase('Ab4'); // false
67. isNil
This snippet can be used to check whether a value is null or undefined.
const isNil = val => val === undefined || val === null;
isNil(null); // true
isNil(undefined); // true
68. isNull
This snippet can be used to check whether a value is null.
const isNull = val => val === null;
isNull(null); // true
69. isNumber
This snippet can be used to check whether a provided value is a number.
function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
isNumber('1'); // false
isNumber(1); // true
70. isObject
This snippet can be used to check whether a provided value is an object. It uses the Object constructor to create an object wrapper for the given value.
If it is already an object, then an object type that corresponds to the given value will be returned. Otherwise, a new object will be returned.
const isObject = obj => obj === Object(obj);
isObject([1, 2, 3, 4]); // true
isObject([]); // true
isObject(['Hello!']); // true
isObject({ a: 1 }); // true
isObject({}); // true
isObject(true); // false
71. isObjectLike
This snippet can be used to check if a value is not nulland that its typeof is “object”.
const isObjectLike = val => val !== null && typeof val === 'object';
isObjectLike({}); // true
isObjectLike([1, 2, 3]); // true
isObjectLike(x => x); // false
isObjectLike(null); // false
72. isPlainObject
This snippet checks whether a value is an object created by the Object constructor.
const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;
isPlainObject({ a: 1 }); // true
isPlainObject(new Map()); // false
73. isPromiseLike
This snippet checks whether an object looks like a Promise.
const isPromiseLike = obj =>
obj !== null &&
(typeof obj === 'object' || typeof obj === 'function') &&
typeof obj.then === 'function';
isPromiseLike({
then: function() {
return '';
}
}); // true
isPromiseLike(null); // false
isPromiseLike({}); // false
74. isSameDate
This snippet can be used to check whether two dates are equal.
const isSameDate = (dateA, dateB) => dateA.toISOString() === dateB.toISOString();
isSameDate(new Date(2010, 10, 20), new Date(2010, 10, 20)); // true
75. isString
This snippet can be used to check whether an argument is a string.
const isString = val => typeof val === 'string';
isString('10'); // true
76. isSymbol
This snippet can be used to check whether an argument is a symbol.
const isSymbol = val => typeof val === 'symbol';
isSymbol(Symbol('x')); // true
77. isUndefined
This snippet can be used to check whether a value is undefined.
const isUndefined = val => val === undefined;
isUndefined(undefined); // true
78. isUpperCase
This snippet can be used to check whether a string is upper case.
const isUpperCase = str => str === str.toUpperCase();
isUpperCase('ABC'); // true
isLowerCase('A3@$'); // true
isLowerCase('aB4'); // false
79. isValidJSON
This snippet can be used to check whether a string is a valid JSON.
const isValidJSON = str => {
try {
JSON.parse(str);
return true;
} catch (e) {
return false;
}
};
isValidJSON('{"name":"Adam","age":20}'); // true
isValidJSON('{"name":"Adam",age:"20"}'); // false
isValidJSON(null); // true
80. last
This snippet returns the last element of an array
const last = arr => arr[arr.length - 1];
last([1, 2, 3]); // 3
81. matches
This snippet compares two objects to determine if the first one contains the same property values as the second one.
const matches = (obj, source) =>
Object.keys(source).every(key => obj.hasOwnProperty(key) && obj[key] === source[key]);
matches({ age: 25, hair: 'long', beard: true }, { hair: 'long', beard: true }); // true
matches({ hair: 'long', beard: true }, { age: 25, hair: 'long', beard: true }); // false
82. maxDate
This snippet can be used to get the latest date.
const maxDate = (...dates) => new Date(Math.max.apply(null, ...dates));
const array = [
new Date(2017, 4, 13),
new Date(2018, 2, 12),
new Date(2016, 0, 10),
new Date(2016, 0, 9)
];
maxDate(array); // 2018-03-11T22:00:00.000Z
83. maxN
This snippet returns the n largest elements from a list. If nis greater than or equal to the list’s length, then it will return the original list (sorted in descending order).
const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
maxN([1, 2, 3]); // [3]
maxN([1, 2, 3], 2); // [3,2]
84. minDate
This snippet can be used to get the earliest date.
const minDate = (...dates) => new Date(Math.min.apply(null, ...dates));
const array = [
new Date(2017, 4, 13),
new Date(2018, 2, 12),
new Date(2016, 0, 10),
new Date(2016, 0, 9)
];
minDate(array); // 2016-01-08T22:00:00.000Z
85. minN
This snippet returns the n smallest elements from a list. If nis greater than or equal to the list’s length, then it will return the original list (sorted in ascending order).
const minN = (arr, n = 1) => [...arr].sort((a, b) => a - b).slice(0, n);
minN([1, 2, 3]); // [1]
minN([1, 2, 3], 2); // [1,2]
86. negate
This snippet can be used to apply the not operator (!) to a predicate function with its arguments.
const negate = func => (...args) => !func(...args);
[1, 2, 3, 4, 5, 6].filter(negate(n => n % 2 === 0)); // [ 1, 3, 5 ]
87. nodeListToArray
This snippet can be used to convert a nodeList to an array.
const nodeListToArray = nodeList => [...nodeList];
nodeListToArray(document.childNodes); // [ <!DOCTYPE html>, html ]
88. pad
This snippet can be used to pad a string on both sides with a specified character if it is shorter than the specified length.
const pad = (str, length, char = ' ') =>
str.padStart((str.length + length) / 2, char).padEnd(length, char);
pad('cat', 8); // ' cat '
pad(String(42), 6, '0'); // '004200'
pad('foobar', 3); // 'foobar'
89. radsToDegrees
This snippet can be used to convert an angle from radians to degrees.
const radsToDegrees = rad => (rad * 180.0) / Math.PI;
radsToDegrees(Math.PI / 2); // 90
90. Random Hexadecimal Color Code
This snippet can be used to generate a random hexadecimal color code.
const randomHexColorCode = () => {
let n = (Math.random() * 0xfffff * 1000000).toString(16);
return '#' + n.slice(0, 6);
};
randomHexColorCode(); // "#e34155"
91. randomIntArrayInRange
This snippet can be used to generate an array with n random integers in a specified range.
const randomIntArrayInRange = (min, max, n = 1) =>
Array.from({ length: n }, () => Math.floor(Math.random() * (max - min + 1)) + min);
randomIntArrayInRange(12, 35, 10); // [ 34, 14, 27, 17, 30, 27, 20, 26, 21, 14 ]
92. randomIntegerInRange
This snippet can be used to generate a random integer in a specified range.
const randomIntegerInRange = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
randomIntegerInRange(0, 5); // 3
93. randomNumberInRange
This snippet can be used to return a random number in a specified range.
const randomNumberInRange = (min, max) => Math.random() * (max - min) + min;
randomNumberInRange(2, 10); // 6.0211363285087005
94. readFileLines
This snippet can be used to read a file by getting an array of lines from a file.
const fs = require('fs');
const readFileLines = filename =>
fs
.readFileSync(filename)
.toString('UTF8')
.split('\n');
let arr = readFileLines('test.txt');
console.log(arr); // ['line1', 'line2', 'line3']
95. Redirect to a URL
This snippet can be used to do a redirect to a specified URL.
const redirect = (url, asLink = true) =>
asLink ? (window.location.href = url) : window.location.replace(url);
redirect('https://google.com');
96. reverse
This snippet can be used to reverse a string.
const reverseString = str => [...str].reverse().join('');
reverseString('foobar'); // 'raboof'
97. round
This snippet can be used to round a number to a specified number of digits.
const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
round(1.005, 2); // 1.01
98. runPromisesInSeries
This snippet can be used to run an array of promises in series.
const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
const delay = d => new Promise(r => setTimeout(r, d));
runPromisesInSeries([() => delay(1000), () => delay(2000)]);
// Executes each promise sequentially, taking a total of 3 seconds to complete
99. sample
This snippet can be used to get a random number from an array.
const sample = arr => arr[Math.floor(Math.random() * arr.length)];
sample([3, 7, 9, 11]); // 9
100. sampleSize
This snippet can be used to get nrandom elements from unique positions from an array up to the size of the array. Elements in the array are shuffled using the Fisher-Yates algorithm
const sampleSize = ([...arr], n = 1) => {
let m = arr.length;
while (m) {
const i = Math.floor(Math.random() * m--);
[arr[m], arr[i]] = [arr[i], arr[m]];
}
return arr.slice(0, n);
};
sampleSize([1, 2, 3], 2); // [3,1]
sampleSize([1, 2, 3], 4); // [2,3,1]
```.#javascript #ES6 #Libraries #JavaScript Snippets for Beginners
