JavaScript Generator next() Method

JavaScript 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

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());

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

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'
];

let geek = GFG(4, list);

console.log(geek.next().value);
console.log(geek.next().value);
console.log(geek.next().value);
console.log(geek.next().value);

Output:

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

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

• Google Chrome
• Firefox
• Opera
• Safari
• Edge

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