How to quickly clear a JavaScript Object?

javascript performance
levik picture levik · Mar 26, 2009 · Viewed 260.4k times · Source

With a JavaScript Array, I can reset it to an empty state with a single assignment:

array.length = 0;

This makes the Array "appear" empty and ready to reuse, and as far as I understand is a single "operation" - that is, constant time.

Is there a similar way to clear a JS Object? I know I can iterate its fields deleting them:

for (var prop in obj) { if (obj.hasOwnProperty(prop)) { delete obj[prop]; } }

but this has linear complexity.

I can also just throw the object away and create a new one:

obj = {};

But "promiscuous" creation of new objects leads to problems with Garbage Collection on IE6. (As described here)

Answer

Wytze picture Wytze · Feb 26, 2013

Well, at the risk of making things too easy...

for (var member in myObject) delete myObject[member];

...would seem to be pretty effective in cleaning the object in one line of code with a minimum of scary brackets. All members will be truly deleted instead of left as garbage.

Obviously if you want to delete the object itself, you'll still have to do a separate delete() for that.

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