Best way to code iterator in javascript - Stack Overflow

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I'm building a plex object in Javascript and I want to expose an iterator over an internal collection of the object.

The only way I can think of is the usual way of exposing iterators in prototype.js :

customObject.each(function (item) { ... })

with the provided function being called by the iterator each for every item in the collection, one after the other.

Do you know any other reliable way? Maybe a way that would let users use the usual foreach construct?

I'm building a plex object in Javascript and I want to expose an iterator over an internal collection of the object.

The only way I can think of is the usual way of exposing iterators in prototype.js :

customObject.each(function (item) { ... })

with the provided function being called by the iterator each for every item in the collection, one after the other.

Do you know any other reliable way? Maybe a way that would let users use the usual foreach construct?

• javascript
• iterator

Share Follow edited Oct 16, 2009 at 23:24 jfs 415k205205 gold badges1k1k silver badges1.7k1.7k bronze badges asked Oct 15, 2009 at 10:51 AlsciendeAlsciende 27k99 gold badges5353 silver badges6868 bronze badges

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2 Answers 2

Sorted by: Reset to default 6

The prototype style function is a good option, though you might also consider something like:

overlayRegistry = function() {
var overlays = [];
var index = 0;


return {
    addOverlay : function(overlay) {
            overlays.push(overlay);
    count : function() {
        return overlays.length;
    },
    reset : function() {
        index = 0;
    },
    next : function() {
        if (index < overlays.length) {
            return overlays[index++];
        } else {
            return null;
                    }
    },
    each : function (callback) {
        for (var index = 0, length = overlays.length; index < length; ++index) {
             callback(overlays[index]);
        }
    }

}
}();

In this case, you can iterate over it in steps while you wait for other events (as was the case behind this structure)

Basically, providing a method like each can work great if all you need is simple iteration, but if you need more control, then something like the above would work (of course, you could do both)

Edit
Added each method

You should use for in instead.

>>> var customObject = {x: 1, y:2}
>>> for (a in customObject) console.log(a, customObject[a])
x 1
y 2

But remember about inherited properties.

>>>Object.prototype.yarrr = function yarrr(){ console.warn('YARRR!') }
>>> for (a in customObject) console.log(a, customObject[a])
x 1
y 2
yarrr()
>>> for (a in customObject) if (customObject.hasOwnProperty(a)) console.log(customObject[a])
x 1
y 2

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