Javascript Array Map Example | Array.prototype.map()

Javascript array map() is an inbuilt function that creates the new array with the results of a provided function on every item in the calling array. The map() function calls the provided callback function once for each element in the array and in order and constructs the new array from the results.

The Javascript array map() function is a  pure function, and it does not modify the existing array instead it will return a new array.

Javascript array map example

The map() method calls the provided function once for each element in an  array, in order.

The  callback function is invoked with the following three arguments: the value of the element, the index of the element, and the Array object that is being traversed. The syntax is the following.

array.map(function(currentValue, index, arr), thisValue)

The currentValue is a required parameter, and it is the current value of the element.

The index is an optional parameter, and it is the index of the current element.

#javascript #array.prototype.map #currentvalue

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Javascript Array Map Example | Array.prototype.map()

Javascript Array From Example | Array.prototype.from()

Javascript array from() is an inbuilt function that creates a new, shallow-copied array instance from an array-like object or iterable object.

The Array .from() lets you develop Arrays from the array-like objects (objects with a length property and indexed items) or  iterable objects ( objects where you can get its items, such as Map and  Set).

The Array from() function was introduced in ECMAScript 2015.

Javascript Array From Example

Array.from() method in Javascript is used to creates a new  array instance from a given array. If you pass a  string to the Array.from() function, then, in that case, every alphabet of the string is converted to an element of the new array instance. In the case of integer values, a new array instance simply takes the elements of the given Array.

The syntax of the Array.from() method is the following.

Syntax

Array.from(arrayLike[, mapFn[, thisArg]])

#javascript #ecmascript #javascript array from #array.prototype.from

Javascript Array Map Example | Array.prototype.map()

Javascript array map() is an inbuilt function that creates the new array with the results of a provided function on every item in the calling array. The map() function calls the provided callback function once for each element in the array and in order and constructs the new array from the results.

The Javascript array map() function is a  pure function, and it does not modify the existing array instead it will return a new array.

Javascript array map example

The map() method calls the provided function once for each element in an  array, in order.

The  callback function is invoked with the following three arguments: the value of the element, the index of the element, and the Array object that is being traversed. The syntax is the following.

array.map(function(currentValue, index, arr), thisValue)

The currentValue is a required parameter, and it is the current value of the element.

The index is an optional parameter, and it is the index of the current element.

#javascript #array.prototype.map #currentvalue

Javascript Array Shift Example | Array.prototype.shift()

Javascript array shift() is an inbuilt function that removes the first item from an array and returns that deleted item. The shift() method changes the length of the array on which we are calling the shift() method. Javascript Array Shift method is not  pure function as it directly modifies the  array.

Javascript Array Shift Example

Javascript shift() method removes the item at the zeroeth index and shifts the values at consecutive indexes down, then returns that removed value.

If we want to remove the last item of an array, use the  Javascript pop() method.

If the length property is 0,  undefined is returned.

The syntax for shift() method is the following.

array.shift()

An array element can be a  string, a number, an  array, a boolean, or any other  object types that are allowed in the Javascript array. Let us take a simple example.

#javascript #array.prototype.shift #javascript pop #javascript shift

Lowa Alice

Lowa Alice

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JavaScript Arrays Tutorial. DO NOT MISS!!!

Learn JavaScript Arrays

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#arrays #javascript #javascript arrays #javascript arrays tutorial

Giles  Goodwin

Giles Goodwin

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Maps in JavaScript

What topics we are going to cover?

  1. What are Maps?
  2. What are the methods used in it and how we can insert or retrieve values to it?
  3. How Maps works, behave with loops and what is happening behind the scenes?

What are Maps?

By the word Map, here I mean another new method which is being used these days in modern JavaScript. Here we are going to see the classic dataType of Map. Mostly Map is getting used in looping concepts that’s a great thing, but if you go directly for all those then you won’t be able to understand the classic dataType of Map.

So let’s fire up our code editor and understand the concepts of Map with some amazing examples.

var myMap = new Map();

This is almost kind of constructional approach, where we create an object from prototype and stuff like that.

What are the methods used in Maps?

Now Map has a lot of properties and I think you should take a look at it, at once. So whenever you gonna type myMap. then you can see a list of methods will be appearing on your screen like- get, set, forEach, values, and bunch of things. So one of the common methods which are being used widely is set and get method and by this time I guess from its name itself you might have guessed it like these are some default setters and getters means it can add values to them and retrieve values from them.

How to insert values in Maps?

Let’s go ahead and try with set() method and have some of the fun together:

Note: They work almost like objects but remember this, Maps are not like objects, they are completely different.

var myMap = new Map();
myMap.set(1, "Ricky"); //myMap.set(any key, any value)
myMap.set(2, "Monty"); //myMap.set(any key, any value)
myMap.set(3, "Henna"); //myMap.set(any key, any value)
myMap.set(4, "Monta"); //myMap.set(any key, any value)
console.log(myMap);

Now if you try to run this code in your editor, then you gonna see an output like this on your screen.

Map(4) { 1 => 'Ricky', 2 => 'Monty', 3 => 'Henna', 4 => 'Monta' }

Notice here, how Maps by default itself is telling you that how many properties you are storing in it and one more thing you can see here they have used => these arrow between its key, value pair to differentiate, and make you understand that they are not your regular objects.

#javascript-development #maps #array-methods #arrays #javascript