How do I enumerate the properties of a JavaScript object? [duplicate]

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Simple enough:

for(var propertyName in myObject) {
   // propertyName is what you want
   // you can get the value like this: myObject[propertyName]
}

Now, you will not get private variables this way because they are not available.

EDIT: @bitwiseplatypus is correct that unless you use the hasOwnProperty() method, you will get properties that are inherited – however, I don’t know why anyone familiar with object-oriented programming would expect anything less! Typically, someone that brings this up has been subjected to Douglas Crockford’s warnings about this, which still confuse me a bit. Again, inheritance is a normal part of OO languages and is therefore part of JavaScript, notwithstanding it being prototypical.

Now, that said, hasOwnProperty() is useful for filtering, but we don’t need to sound a warning as if there is something dangerous in getting inherited properties.

EDIT 2: @bitwiseplatypus brings up the situation that would occur should someone add properties/methods to your objects at a point in time later than when you originally wrote your objects (via its prototype) – while it is true that this might cause unexpected behavior, I personally don’t see that as my problem entirely. Just a matter of opinion. Besides, what if I design things in such a way that I use prototypes during the construction of my objects and yet have code that iterates over the properties of the object and I want all inherited properties? I wouldn’t use hasOwnProperty(). Then, let’s say, someone adds new properties later. Is that my fault if things behave badly at that point? I don’t think so. I think this is why jQuery, as an example, has specified ways of extending how it works (via jQuery.extend and jQuery.fn.extend).

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