adding item to array in jquery

Question

I know this code is correct, I did not write it. I am trying to understand what the code is doing.

create variable
loop through unordered list's children
set cssClass = class name
if the cssClass is not in myarray, add it to myarray

I am familiar with other ways to check to see if an item is in an array, and familiar with other ways to add an item to an array, but this method confuses me. Do other languages support this type of syntax?

    var myarray = [];
    $(".somelist > li").each(function() {
    var cssClass = $(this).attr("class");

    //This part below is CONFUSING
    if(!myarray[cssClass]) {
         myarray[cssClass] = true;
    }
});

myarray = [] should be myarray = {} if any of the class names are non-integers. — Rob W
– Rob W, Commented Oct 4, 2011 at 14:41
The conusing and stupid bit is that myarray is an array instead of an object. Of course arrays are also objects, it's just not used as an array — Raynos
– Raynos, Commented Oct 4, 2011 at 14:41
This link may be helpful to others. javascriptkata.com/2007/03/29/how-to-use-javascript-hashes — user584583
– user584583, Commented Oct 4, 2011 at 16:50
another link blog.persistent.info/2004/08/javascript-associative-arrays.html — user584583
– user584583, Commented Oct 4, 2011 at 16:57

Dave Newton · Accepted Answer · 2011-10-04 14:40:13Z

2

If the hash/map doesn't contain an entry for the given class, add it.

It's creating a collection of all the classes used by list items in the somelist class.

answered Oct 4, 2011 at 14:40

Dave Newton

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Comments

ipr101 · Accepted Answer · 2011-10-04 14:46:33Z

1

1 if(!myarray[cssClass]) {
2         myarray[cssClass] = true;
    }

Here's a brief outline of what's happening, the myarray variable is used as a hash -

1 - Checks to see if the current class name is in the array. myarray[cssClass] will return a 'falsy' value if the class name is not conatined in the array.

2 - If the class is not in the array, add it to the array and set it's value to true

edited Oct 4, 2011 at 14:46

answered Oct 4, 2011 at 14:40

ipr101

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Comments

genesis · Accepted Answer · 2011-10-04 14:39:00Z

1

In this case, it will be false only if it's first occurence of that array. When it's second loop and class is the same, it won't change it to true again. It makes no sense though. This code is synonym of

    var myarray = [];
    $(".somelist > li").each(function() {
    var cssClass = $(this).attr("class");
    myarray[cssClass] = true;
});

answered Oct 4, 2011 at 14:39

genesis

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Comments

Bas Slagter · Accepted Answer · 2011-10-04 14:40:27Z

1

If the array does not contain an entry with the key represented by the cssClass variable it will add it and set the value of that key to true. If it already exists, it stays true...so

if(!myarray[cssClass]))

returns false if there is no key with the value that is set to the cssClass variable. I don't know the context of this code but from this point it seems a bit useless.

answered Oct 4, 2011 at 14:40

Bas Slagter

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