javascript - Get single yield value from iteratorgenerator - Stack Overflow

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I need entity that return incrementing integer after each call.

For example I have code.

var id = 0; //global variable =(

function foo() {
   ....
   console.log("Your unique ID is " + id++);
   ....
}

and it works fine. But I want to use generators for this work.

Something like:

function* getId() {
   var id = 0;
   while (true) {
       yield id++;
   }
}

 function foo() {
   ....
   console.log("Your unique ID is " + getId());
   ....
}

But result is only empty figure quotes. What i missed? Maybe using generators is a bad idea for this kind of generation?

I need entity that return incrementing integer after each call.

For example I have code.

var id = 0; //global variable =(

function foo() {
   ....
   console.log("Your unique ID is " + id++);
   ....
}

and it works fine. But I want to use generators for this work.

Something like:

function* getId() {
   var id = 0;
   while (true) {
       yield id++;
   }
}

 function foo() {
   ....
   console.log("Your unique ID is " + getId());
   ....
}

But result is only empty figure quotes. What i missed? Maybe using generators is a bad idea for this kind of generation?

• javascript
• node.js
• ecmascript-6
• generator

Share Improve this question Follow edited May 8, 2016 at 22:38 Bergi 666k161161 gold badges1k1k silver badges1.5k1.5k bronze badges asked May 8, 2016 at 21:42 Stepan LoginovStepan Loginov 1,76755 gold badges2424 silver badges5555 bronze badges

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3 Answers 3

Sorted by: Reset to default 9

Your getId is a generator function that creates a generator, instead of advancing one and getting its values.
You should do something like

function* IdGenerator() {
    var i = 0;
    while (true) {
        yield i++;
    }
}
IdGenerator.prototype.get = function() {
    return this.next().value;
};

var ids = IdGenerator();
function foo() {
    …
    console.log("Your unique ID is " + ids.get());
    …
}

Here are the things I can tell are wrong:

• you're resetting the id value on every function call.
• for the generator to output the value of next iteration you need to generate the iterator, then you can access its next().value

Here's an example:

function* getId() {
 var id = 0;
    while (true) {
      yield id++;
    };
}

var itId = getId();

function foo() {
  console.log("Your unique ID is " + itId.next().value);
}

foo()
foo()

If you..

• don't want to pollute your namespace
• want short code

Then maybe an IIFE closing over the incremented variable will serve you better than a function* in this case

var getId = (function () {
    var i = 0;
    return () => i++;
}());

getId(); // 0
getId(); // 1
getId(); // 2

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