What is the use of Generator function in js

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What is the Generator function and what does it do?

The Generator function can be said to be the specific implementation of the Iterator interface. The most important feature of Generator is that it can control the execution of functions.

Function * foo (x) {let y = 2 * (yield (x + 1)) let z = yield (y / 3) return (x + y + z)} let it = foo (5) console.log (it.next ()) / / = > {value: 6, done: false} console.log (it.next (12)) / / = > {value: 8, done: false} console.log (it.next (13)) / = > {value: 42, done: true}

The above example is a Generator function, and let's analyze its execution:

First, when the Generator function is called, it returns an iterator.

When the first next is executed, the passing parameter is ignored and the function is paused at yield (x + 1), so 5 + 1 = 6 is returned.

When the second next is executed, the parameter passed in is equal to the return value of the previous yield, and if you do not pass the parameter, yield always returns undefined. At this point let y = 2 * 12, so the second yield equals 2 * 12 / 3 = 8

When the third next is executed, the passed parameters are passed to z, so z = 13, x = 5, y = 24, and the sum equals 42

Generator function generally does not see much, in fact, it has something to do with it, and will generally be used in conjunction with the co library. Of course, we can solve the problem of callback hell through the Generator function.

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