how to fetch array keys with jQuery

Question

Good afternoon  I have an array with some keys  and values in them  I then need to fetch the array keys and not the data in them  I want to do this with jQuery  I know for example that PHP has a function called array keys    which takes the array as a parameter and gives you an array back with each key in each index   This is what I came up with  and it works    the only problem is that it seems so unefficent   var foo       foo  alfa      first item   foo  beta      second item    for  var key in foo        console log key       This will output   alfa beta   But is there any predefined function for this  as in PHP or any other more effective way of getting this

User · Answer

I use something like this function I created...

Object.getKeys = function(obj, add) {
    if(obj === undefined || obj === null) {
        return undefined;
    }
    var keys = [];
    if(add !== undefined) {
        keys = jQuery.merge(keys, add);
    }
    for(key in obj) {
        if(obj.hasOwnProperty(key)) {
                keys.push(key);
        }
    }
    return keys;
};

I think you could set obj to self or something better in the first test. It seems sometimes I'm checking if it's empty too so I did it that way. Also I don't think {} is Object.* or at least there's a problem finding the function getKeys on the Object that way. Maybe you're suppose to put prototype first, but that seems to cause a conflict with GreenSock etc.

User · Answer

Use an object  key value pairs  the nearest JavaScript has to an associative array  for this and not the array object  Other than that  I believe that is the most elegant way  var foo       foo  alfa      first item   foo  beta      second item    for  var key in foo            console log key       Note  JavaScript doesn t guarantee any particular order for the properties  So you cannot expect the property that was defined first to appear first  it might come last   EDIT   In response to your comment  I believe that this article best sums up the cases for why arrays in JavaScript should not be used in this fashion -    Associative Arrays  considered Harmful

User · Answer

console log  Object keys    a  1  b  2

User · Answer

you can use the each function   var a       a  alfa     0  a  beta     1    each a  function key  value          alert key        it has several nice shortcuts tricks  check the gory details here

User · Answer

Using jQuery  easiest way to get array of keys from object is following     map obj  function element index   return index     In your case  it will return this array    alfa    beta

User · Answer

Don t Reinvent the Wheel  Use Underscore  I know the OP specifically mentioned jQuery but I wanted to put an answer here to introduce people to the helpful Underscore library if they are not aware of it already   By leveraging the keys method in the Underscore library  you can simply do the following      keys foo      gt    alfa    beta     Plus  there s a plethora of other useful functions that are worth perusing

[jquery] how to fetch array keys with jQuery?

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