Iterators tutorial in Advance JavaScript

October 17, 2024

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    <title>Iterators Advance JavaScript</title>
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    <script>
        //Example 1 :
        let numbers = [100, 200, 300, 400, 500];
        console.log(typeof numbers[Symbol.iterator]);

        let iter = numbers[Symbol.iterator]();
        console.log(iter);
        console.log(iter.next());   //When next value is present then in output(console), "done: false" will show
        // console.log(iter.next().value); //We can print direct value 
        console.log(iter.next());
        console.log(iter.next());
        console.log(iter.next());   //When next value is not present then in output(console), "done: true" will show

        let result = iter.next();
        while (!result.done) {
            console.log(result.value);
            result = iter.next();
        }

        //Example 2 :
        let str = "Hello World";
        let iterTwo = str[Symbol.iterator]();
        let resultTwo = iterTwo.next();
        while (!resultTwo.done) {
            console.log(resultTwo.value);
            resultTwo = iterTwo.next();
        }

        //We can also use for..of loop for above Example
        for (var char of str) {
            console.log(char);
        }

        //Example 3 : Creating User defined Iterator Function and take Control in our Hand as shown below :
        function numberIterator(arr) {
            var nextNum = 0;
            return {
                next() {
                    if (nextNum < arr.length) {
                        return {
                            value: arr[nextNum++],
                            done: false
                        }
                    }
                    else {
                        return {
                            done: true
                        }
                    }
                }
            }
        }

        let numbersTwo = [100, 200, 300, 400, 500];
        let num = numberIterator(numbersTwo);
        console.log(num.next());
        num.next();
        console.log(num.next());
        console.log(num.next().value);
        console.log(num.next());
        console.log(num.next());
    </script>
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