How do I declare and access an array of objects in JavaScript?

Question

I have the following code, with the intention of defining and using a list of objects, but I get an 'undefine' for post_title. What am I doing wrong? I don't want to name the array as a property of an object, I just want a collection/array of objects.

var templates = [{ "ID": "12", "post_title": "Our Title" }
    , { "ID": "14", "post_title": "pwd" }];
function templateOptionList() {
    for(var t in templates) {
        console.log(t.post_title);
    }
}
$(function () {
    templateOptionList();
});

I hope you don't mind, but I've edited the question title/tags to remove references to JSON (this isn't JSON: JSON is a string representation of object/array data that just looks like object/array literal syntax in JavaScript). — nnnnnn
– nnnnnn, Commented Dec 5, 2011 at 4:02

icktoofay · Accepted Answer · 2011-12-05 03:54:21Z

5

You're defining the array correctly, but that's not how you iterate over an array in JavaScript. Try this:

function templateOptionList() {
    for(var i=0, l=templates.length; i<l; i++) {
        var t=templates[i];
        console.log(t.post_title);
    }
}

A nicer (albeit a little slower) way of doing this that only works in newer browsers would be to use Array.forEach:

function templateOptionList() {
    templates.forEach(function(t) {
        console.log(t.post_title);
    });
}

answered Dec 5, 2011 at 3:54

icktoofay

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5 Comments

ProfK Over a year ago

How much newer must a browser be? I'm targeting the WordPress market here, and who knows how backward their targets are.

icktoofay Over a year ago

@ProfK: Find Array.prototype.forEach in here. It looks like most current browsers support it except for IE 8 and below.

nnnnnn Over a year ago

In other words a significant percentage of users can't use Array.prototype.forEach...

icktoofay Over a year ago

You can shim it if you want, but it's trivial to iterate without it here.

Ryan Gibbons Over a year ago

Circling back around, realized this was answered before my post, SO didn't remind me fast enough. Anyways, check out this answer for a quickly on why not use to use for .. in on arrays stackoverflow.com/questions/500504/…

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