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JavaScript Array unshift() Method

  • Last Updated : 25 Jun, 2020

Below is the example of Array unshift() method.

  • Example:




    <script>
    function func() { 
          
        // Original array 
        var array = ["GFG", "Geeks", "for", "Geeks"]; 
      
        // Checking for condition in array 
        var value = array.unshift("GeeksforGeeks"); 
      
        document.write(value);
        document.write("<br />"); 
        document.write(array); 
      
    func();
    </script>
  • Output:
    5
    GeeksforGeeks,GFG,Geeks,for,Geeks

The arr.unshift() method is used to add one or more elements to the beginning of the given array. This function increases the length of the existing array by the number of elements added to the array.

Syntax:

array.unshift(element1, element2, ..., elementX)

Parameters: This method accept a single parameters.

  • element: This parameter elements to be added at the beginning of the array.

Return value: This function returns the new length of the array after inserting the arguments at the beginning of the array.



Below examples illustrate the JavaScript Array unshift() method:

  • Example 1: In this example the function unshift() adds 28 and 65 to the front of the array.
    var arr = [23,76,19,94];
    document.write(arr.unshift(28,65));
    document.write(arr);
    

    Output:

    6
    28,65,23,76,19,94
    
  • Example 2: In this example the shift() method tries to remove the first element of the array, but the array is empty, therefore it returns undefined.
    var arr = [23,76,19,94];
    document.write(arr.unshift());
    document.write(arr);
    

    Output:

    4
    23,76,19,94

Code for the above method is provided below:
Program 1:




// JavaScript to illustrate unshift() function
<script>
function sayHello() {
    var arr = [23,76,19,94];
       
    // Adding elements to the front of the array
    document.write(arr.unshift(28,65));
    document.write("<br>");
    document.write(arr);
}
sayHello();
</script>

Output:

34
234,567,4

Program 2:




// JavaScript to illustrate unshift() function
<script>
function sayHello() {
    var arr = [23,76,19,94];
       
    // Adding elements to the front of the array
    document.write(arr.unshift(28,65));
    document.write("<br>");
    document.write(arr);
}
sayHello();
</script>

Output:

4
23,76,19,94

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

  • Google Chrome
  • Microsoft Edge
  • Mozilla Firefox
  • Safari
  • Opera



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