js adding a value to a element in an array

Question

I found some answers to similiar questions but I'm still not getting it.

but I hope it's a short problem so I dont make too much trouble! ;-)

I have a js array

arr = [ a, b, c]

How can i add value to this elements dynamically? For example I want that each element get the value true

So it should look like this afterwards:

arr = [ a = true, b = true, c = true];

I tried the following: (using jquery framework)

$.each(arr, function(i){
                arr[i] = true;
            });

but then I just get

arr = [ true, true, true]

hope someone can help me! thanx

bobince · Accepted Answer · 2009-11-23 13:21:38Z

4

arr = [ a = true, b = true, c = true];

That's a different type of data structure you're looking for: not an array, but a mapping. (PHP makes arrays and mappings the same datatype, but that's an unusual quirk.)

There's not quite a general-purpose mapping in JavaScript, but as long as you're using strings for keys and you take care to avoid some of the built-in JavaScript Object member names, you can use an Object for it:

var map= {'a': true, 'b': true, 'c': true};
alert(map['a']); // true
alert(map.a); // true

ETA:

if i have an array how can i make it to look like ["required": true, "checklength": true]?

var array= ['required', 'checklength'];

var mapping= {};
for (var i= array.length; i-->0;) {
    var key= array[i];
    mapping[key]= true;
}

alert(mapping.required); // true
alert('required' in mapping); // also true
alert('potato' in mapping); // false

edited Nov 23, 2009 at 13:21

answered Nov 23, 2009 at 11:57

bobince

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3 Comments

Justin Johnson Over a year ago

For the benefit of the OP and other novices, please note that using this method, there is no length property as you are accustomed to with normal, indexed arrays. Also, iteration over this data type must be done using for..in (w3schools.com/jS/js_loop_for_in.asp), as opposed to an array which should be iterated over using the standard for structure (w3schools.com/jS/js_loop_for.asp).

Stefan Over a year ago

hey. thank you but i still dont know how to add an value to a element as i descriped above. u just show me how to set up a object with value direct ..but if i have an array (or object... ) so ["required", "checklength"] (firebug) how can i make it to look like ["required": true, "checklength": true]? maybe my english isnt good enough to descripe it clearly! :-(

Fabien Ménager Over a year ago

An array in JS with named keys is an object. He answered your question.

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