concat method is used to merge two arrays. As a result, it returns a new array instead of modifying the existing array.
Let’s look at an example using the
concat method. We have two arrays named
fruits2. They both contain strings that correspond to a fruit.
const fruits1 = ['apple', 'banana', 'grapes']; const fruits2 = ['melons', 'watermelon']; const combinedFruits = fruits1.concat(fruits2); console.log(combinedFruits); //[ 'apple', 'banana', 'grapes', 'melons', 'watermelon' ]
Now let’s look at an example using the spread syntax.
const fruits1 = ['apple', 'banana', 'grapes']; const fruits2 = ['melons', 'watermelon']; const combinedFruits = [...fruits1, ...fruits2]; console.log(combinedFruits); //[ 'apple', 'banana', 'grapes', 'melons', 'watermelon' ]
In this example, we created a new array and assigned it to the variable combinedFruits. We then took the two fruits array and used the spread them out in the array. We used the … syntax to spread out the contents of the fruits array into the new array.
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By the word Array methods, I mean the inbuilt array functions, which might be helpful for us in so many ways. So why not just explore and make use of them, to boost our productivity.
Let’s see them together one by one with some amazing examples.
_fill()_method changes all elements in an array to a static value, from a start index (default
_0_) to an end index (default
_array.length_). It returns the modified array.
In simple words, it’s gonna fill the elements of the array with whatever sets of params, you pass in it. Mostly we pass three params, each param stands with some meaning. The first param value: what value you want to fill, second value: start range of index(inclusive), and third value: end range of index(exclusive). Imagine you are going to apply this method on some date, so that how its gonna look like eg: array.fill(‘Some date’, start date, end date).
NOTE: Start range is inclusive and end range is exclusive.
Let’s understand this in the below example-
//declare array var testArray = [2,4,6,8,10,12,14]; console.log(testArray.fill("A"));
When you run this code, you gonna see all the elements of
testArray will be replaced by
In this post I’ll be covering how to perform the create, read update and delete operations using arrays, some common functions that come with the Array prototype and also how to implement them.
Before we jump into the juicy bits of Arrays, lets quickly gloss over what they are. Arrays
Array.prototypethat includes a wide variety useful functions that can be called from arrays or
If you’re not familiar with the term CRUD it stands for Create, Read, Update and Delete. In this section we’ll go through each one of these operations and cover different ways you can perform each one.
There are several ways you can create an Array but the most common ways are by using
Lets take a look at each one with examples
The array literal is the most common way of creating an array. It uses the square brackets as a notion of a container followed by comma separated values inside the square brackets. The following examples show how to use the array literal syntax and how arrays are untyped i.e. can contain elements of different types.
Another way to create an array is through the Array constructor.
const myArray = new Array();
Using the Array constructor, as shown above, is the same as creating an array with the array literal syntax. i.e.
// The following two lines behave exactly the same way i.e. both create an empty arrays const myArray = new Array(); const myOtherArray = ;
The array constructor, however, is able to receive arguments that allow it to behave in different ways depending on the number and type of arguments passed to it.
const myArray = new Array(5);
Note: If you want to define the array with a specified size, as shown above, the argument passed must be a numeric value. Any other type would be considered as the first element that’ll be placed in the array.
As stated earlier, these two ways are the most common ways of creating arrays that you’ll see and use 99% of the time. There are a few other ways but we won’t dive deep into how they work. They are
const someArray = […someOtherArray]
The callback now receives an accumulator (it accumulates all the return values. Its value is the accumulation of a previously returned accumulations), a current value, a current index, and finally, the whole array.
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.
The syntax of the Array.from() method is the following.
Array.from(arrayLike[, mapFn[, thisArg]])