javascript - Get single yield value from iteratorgenerator

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?

Share Improve this question edited May 8, 2016 at 22:38 Bergi 666k161 gold badges1k silver badges1.5k bronze badges asked May 8, 2016 at 21:42 Stepan Loginov 1,7675 gold badges24 silver badges55 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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javascript - Get single yield value from iteratorgenerator - Stack Overflow

3 Answers 3

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