Using the function* Declaration in JavaScript
The function* declaration is used to define a generator that returns a Generator object. Generators are very powerful for asynchronous programming as they aim to resolve callback problems.
In a generator, the yield keyword is used instead of return. The yield statement suspends the function’s execution and sends a value back to the caller, but retains enough state to enable the function to resume from the last execution state. The function, therefore, continues execution immediately after the last yield run. The next() method is used to return an object with two properties, done and value, and can be used to proceed to the next state of the generator.
Syntax:
function* function_name(param1, param2...)
{
function body
}
The below examples demonstrate the use of the function* declaration.
Example 1: This example shows the declaration of a function * and the use of yield and next().
JavaScript
<script>
function * generator(i) {
yield i;
yield i + 50;
yield i + 100;
}
const generate = generator(50);
let nextValObj = generate.next();
console.log(nextValObj.value);
console.log(generate.next().value);
console.log(generate.next().value);
console.log(generate.next().value);
</script>
|
Output:
50
100
150
undefined
Example 2: This example shows the declaration of a function * and the use of yield and next().
JavaScript
<script>
function * powerup(n) {
for (let num = n; ; num *= n) {
yield num;
}
}
for (let power of powerup(5)) {
if (power > 1024)
break ;
console.log( "Yielded:" , power)
}
</script>
|
Output:
Yielded: 5
Yielded: 25
Yielded: 125
Yielded: 625
Last Updated :
30 Dec, 2022
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