How to get array length without length property

Question

Even though we can use array.length to get array length it may go wrong in a case like below..

var a = [2, 4, "bang", undefined, NaN, 5]; 
a.length = 0; 
document.write(a.length);

counting with for in may also go wrong if the array has additional properties defined.

So is there a way to get array length dynamically?

Not sure this really deserves the downvotes, is it not a reasonable (if a tad simple) question? — Clive, Dec 30 '14 at 12:22
I'm reading again and again and I couldn't find the logic behind your `a.length = 0`!!! — LcSalazar, Dec 30 '14 at 12:31
I didn't know `array.length = 0` changes the true array length. sorry.. @LcSalazar — Sampath Liyanage, Dec 30 '14 at 12:32
Not an exact duplicate, but worth reading: [*Empty an array in JavaScript?*](http://stackoverflow.com/questions/1232040/empty-an-array-in-javascript/1234337#1234337). — RobG, Dec 30 '14 at 12:36

score 2 · Accepted Answer · answered Dec 30 '14 at 12:20

Calling

a.length = 0;

Does remove all elements from the array

console.log(a[2]) // undefined

Therefore, your array no longer contains any elements.

Also remember that setting properties that are not coercible to an integer (a.something = 'blah') will not affect the length property.

score 1 · Answer 2 · answered Dec 30 '14 at 12:20

1

If you do, a.length = 0, It will remove all array elements, and the length will be 0. Does it show any other value?

answered Dec 30 '14 at 12:20

dr_dev

score 1 · Answer 3 · answered Dec 30 '14 at 12:20

1

a.length is always correct. a.length = 0; TRUNCATES all data from array.

answered Dec 30 '14 at 12:20

Ginden

3 Answers3