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Editor to share with you what yield means in es6, I believe most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

In es6, yield is the keyword that the generator uses to pause itself internally; yield is followed by a generator function or other iterable object, and the return value of the yield expression is the return value of the iterable object after it is iterated. The syntax is "function*gen () {yield expression}".

This tutorial operating environment: windows10 system, ECMAScript version 6. 0, Dell G3 computer.

What does yield mean in es6

Yield is the keyword that the Generator (generator) in ES6 uses to pause itself internally.

Note the word "inside" that the generator function cannot be paused by external logic, but only by itself via yield.

The yield keyword can be followed by a variable or can be used alone. If yield is followed by a variable (we can call it an yield expression), when the generator function resumes running again after a pause, the passed parameter participates in the subsequent logical operation as the value of the overall yield expression

When yield is not followed by a variable, the yield used alone is only used as a pause generator function, and the parameters passed in after the generator resumes operation participate in the subsequent operation as the value of yield.

Give an example

Step 1, construct a generator function.

Function* numbers () {yield 1; yield 2; return 'numbers';}

Step 2, do a proxy on the outer layer of the generator function above.

Function* delegate () {var str = yield* numbers (); console.log (str); yield 3; return 'delegate';}

Step 3, construct an iterator.

Var iterator = delegate ()

Step 4, output the iteration results.

/ * first output * {value: 1, done: false} * / console.log (iterator.next ()) / / first output / * second output * {value: 2, done: false} * / console.log (iterator.next ()) / / second output / * third output * numbers * {value: 3 Done: false} * / console.log (iterator.next ()) / / third output / * fourth output result * {value: 'delegate', done: true} * / console.log (iterator.next ()) / / fourth output

Output result description

On the third output, two lines are output. The first line is the output of console.log (str) in the delegate function, and the value is the return value of the numbers function.

On the fourth output, a line is output, where the value value is the return value of the delegate function. At this point, the done property is true.

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