11, Jan 2023
How to initialize an array’s length in JavaScript?
How to initialize an array's length in JavaScript?
How to initialize an array’s length in JavaScript?

In JavaScript, you can initialize an array’s length using the Array() constructor, or the array literal notation [].

Here are a few examples:

Using the Array() constructor:

let myArray = new Array(5); // creates an array with length of 5
console.log(myArray.length); // prints 5

Using the array literal notation:

let myArray = new Array(5);
console.log(myArray.length); // prints 5

Please note that both examples will create an array with a length of 5, but with no elements in it. You can also fill the array with values if you want, for example:

let myArray = new Array(5).fill(0);
console.log(myArray); // prints [0,0,0,0,0]

It’s important to know that the length property of an array is a dynamic property, this means that if you add or remove elements from the array, the length will change accordingly.

let myArray = [];
console.log(myArray.length); // prints 0
console.log(myArray.length); // prints 1

Another way to set a length of an array is by using the .length property, and just set the number you want it to be.

let myArray = [1,2,3,4,5];
myArray.length = 2;
console.log(myArray); // prints [1,2]

This truncates the array, keeping only the first two elements, and removing the rest.

It’s worth noting that when using .length property, it can be set to a smaller number, that will truncate the array, or to a larger number, that will set undefined values to the added positions.

Initializing the array with a specific length can be useful when you know in advance the size of the data you’ll be working with, it will also allow to work with indexes more efficiently.

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