How to get JavaScript hash table count? [duplicate]

Question

Possible Duplicate:
Length of Javascript Associative Array

hash_table = {a: 131, b: 222, c:313}

The length method is not working of course since it will be confused with a key.

So how do I do it?

From the duplicate question, a useful answer that's not here. Use underscore's size, _.size(). stackoverflow.com/a/11346637/1684480 — Thaddeus Albers
– Thaddeus Albers, Commented Sep 7, 2013 at 6:19

qiao · Accepted Answer · 2012-01-02 14:55:02Z

85

Object.keys will return all the keys in the object as a list, then use length to get the length.

example:

Object.keys(hash_table).length

NOTE that this is ECMA 5 and may not be available in some browsers. see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/keys for full document.

answered Jan 2, 2012 at 14:55

qiao

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4 Comments

rsk82 Over a year ago

Would it return also inherited properties ?

qiao Over a year ago

Nope, it will return only own properties.

Irongaze.com Over a year ago

As I understand it, Object.keys is not supported in IE8 and lower, so beware...

Plaute Over a year ago

Always supported in 2017 :)

simonecampora · Accepted Answer · 2012-01-02 16:36:55Z

1

var count = 0; for ( property in hash_table ) count++;

edited Jan 2, 2012 at 16:36

answered Jan 2, 2012 at 15:11

simonecampora

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4 Comments

Felix Kling Over a year ago

JSON is a data exchange format and has nothing to do with JavaScript, besides the name and similar syntax. JavaScript does not have "Associative Arrays", only arrays.

simonecampora Over a year ago

thanks for your feedbacK: I have edited my answer accordingly!

Felix Kling Over a year ago

Still, what do you mean by "using Arrays in associative fashion"? The length property is only updated for numerical properties,i.e. arr[0] = 42.. Non-numerical properties do not update length and should not be used for arrays as it is just confusing.

simonecampora Over a year ago

please find more detailes here: en.wikipedia.org/wiki/JavaScript_syntax#Array "One can use the object declaration literal to create objects that behave much like associative arrays" but indeed I was wrong. I will edit my answer

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