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JavaScript Array fill() Method

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The Javascript arr.fill() method is used to fill the array with a given static value. The value can be used to fill the entire array or it can be used to fill a part of the array. 

Syntax:

arr.fill(value, start, end)

Parameters: This method accepts three parameters as mentioned above and described below: 

  • value: It defines the static value with which the array elements are to be replaced.
  • start: (Optional): It defines the starting index from where the array is to be filled with the static value. If this value is not defined the starting index is taken as 0. If the start is negative then the net start index is length+start.
  • end :(Optional): This argument defines the last index up to which the array is to be filled with the static value. If this value is not defined then by default the last index of the i.e arr. length – 1 is taken as the end value. If the end is negative, then the net end is defined as length+end.

Return value: This method does not return a new array. Instead of it modifies the array on which this method is applied.

Below is an example of the Array fill() method to fill with a single digit. 

Example 1: In this example, the array will be filled with 87 at all the indexes using the fill() method.

JavaScript

// JavaScript code for fill() method
function func() {
    let arr = [1, 23, 46, 58];
 
    // fill array with 87
    arr.fill(87);
    console.log(arr);
}
func();

                    

Output
[ 87, 87, 87, 87 ]

Example 2: In this example the method fill() fills the array from index 1 to 2 one less than the upper index with 87, replacing all the initial values present in the array. 

JavaScript

// JavaScript code for fill() method
function func() {
    let arr = [1, 23, 46, 58];
 
    // here value = 87, start index=1 and
    // and last index = 3
    arr.fill(87, 1, 3);
    console.log(arr);
}
func();

                    

Output
[ 1, 87, 87, 58 ]

Example 3: In this example the method fill() fills the array from index 1 to 3 with 87, replacing all the initial values present in the array.

JavaScript

// JavaScript code for fill() method
function func() {
    let arr = [1, 23, 46, 58];
 
    // Here value = 87, start index=1
    arr.fill(87, 2);
    console.log(arr);
}
 
func();

                    

Output
[ 1, 23, 87, 87 ]

We have a complete list of Javascript Array methods, to check those please go through this Javascript Array Complete reference article.

Supported Browsers: The browsers supported by the JavaScript Array fill() method are listed below: 

  • Google Chrome 45.0
  • Microsoft Edge 12.0
  • Mozilla Firefox 31.0
  • Safari 7.1
  • Opera 32.0

We have a Cheat Sheet on Javascript where we covered all the important topics of Javascript to check those please go through Javascript Cheat Sheet-A Basic guide to JavaScript



Last Updated : 07 Jul, 2023
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