up vote 1 down vote favorite 
var arr = [-3, -34, 1, 32, -100];

How can I remove all items and just leave an empty array?

And is it a good idea to use this?

arr = [];

Thank you very much!

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3  
You answered your own question, at least the first one! – Stephen Aug 27 '10 at 16:17

7 Answers

up vote 13 down vote

If there are no other references to that array, then just create a new empty array over top of the old one:

array = [];

If you need to modify an existing array—if, for instance, there's a reference to that array stored elsewhere:

var array1 = [-3, -34, 1, 32, -100];
var array2 = array1;

// This.
array1.length = 0;

// Or this.
while (array1.length > 0) {
    array1.pop();
}

// Now both are empty.
assert(array2.length == 0);
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This is the answer. I wrote pretty much the same before spotting that John had already done it. – Tim Down Aug 27 '10 at 22:53
up vote 2 down vote

one of those two:

var a = Array();
var a = [];
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arr = [] is recommended as it takes up less space (code wise). – Zoidberg Aug 27 '10 at 16:18
1  
And it is sexier. – Stephen Aug 27 '10 at 16:20
1  
@Stephen: [] turns you on? – BoltClock♦ Aug 27 '10 at 16:21
1  
literally. ::drum-roll rim-shot:: – Stephen Aug 27 '10 at 16:24
up vote 2 down vote

Just as you say:

arr = [];
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up vote 0 down vote

Using arr = []; to empty the array is far more efficient than doing something like looping and unsetting each key, or unsetting and then recreating the object.

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up vote 0 down vote

While you can set it to a new array like some of the other answers, I prefer to use the clear() method as such:

array.clear();
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up vote 0 down vote

The following article should answer part 2. http://stackoverflow.com/questions/864516/what-is-javascript-garbage-collection

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up vote 0 down vote

Out of box idea:

while(arr.length) arr.pop();
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Will work, but is needlessly inefficient. arr.length = 0 will be quicker and easier to read. – Tim Down Aug 27 '10 at 22:52

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