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JavaScript Generator.prototype.next() Method

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  • Last Updated : 29 Dec, 2022
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The Generator.prototype.next() method is an inbuilt method in JavaScript that is used to return an object with two properties done and value. 

Syntax:

gen.next( value );

Parameters: This function accepts a single parameter as mentioned above and described below:

  • value: This parameter holds the value to be sent to the generator.

Return value: This method returns an object containing two properties:

  • done: It has the value
    • true – for the iterator which is past the end of the iterated sequence.
    • false – for the iterator which is able to produce the next value in the sequence.
  • value: It contains any JavaScript value which is returned by the iterator.

The below examples illustrate the Generator.prototype.next() method in JavaScript: 

Example 1: In this example, we will create a generator and then apply the Generator.prototype.next() method and see the output.

javascript




<script>
    function* GFG() {
    yield "GeeksforGeeks";
    yield "JavaScript";
    yield "Generator.prototype.next()";
    }
      
    const geek = GFG();
    console.log(geek.next());    
    console.log(geek.next());    
    console.log(geek.next());    
    console.log(geek.next());
</script>

Output:

Object { value: "GeeksforGeeks", done: false }
Object { value: "JavaScript", done: false }
Object { value: "Generator.prototype.next()", done: false }
Object { value: undefined, done: true }

Example 2: In this example, we will create a generator and then apply the Generator.prototype.next() method and see the output.

javascript




<script>
    function* GFG(len, list) {
        let result = [];
        let val = 0;
          
        while (val < list.length) {
            result = [];
            let i = val
            while(i < val + len)
            {
                if (list[i]) {
                    result.push(list[i]);
                }
            i+=1
            }
          
            yield result;
            val += len;
        }
    }
    list = [
        'geeks1','geeks2','geeks3',
        'geeks4','geeks5','geeks6',
        'geeks7','geeks8','geeks9',
        'geeks10','geeks11'
    ];
      
    var geek = GFG(4, list);            
          
    console.log(geek.next().value);    
    console.log(geek.next().value);    
    console.log(geek.next().value);    
    console.log(geek.next().value);
</script>

Output:

geeks1,geeks2,geeks3,geeks4
geeks5,geeks6,geeks7,geeks8
geeks9,geeks10,geeks11
undefined

We have a complete list of Javascript Generator function methods, to check those please go through the Javascript Generator Complete Reference article.

Supported Browsers: The browsers supported by Generator.prototype.next() method are listed below:

  • Google Chrome
  • Firefox
  • Opera
  • Safari
  • Edge

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