Question

I have an array of objects. Each object has, among others, an ID attribute. I want to find the index in the array of the object with a specific ID. Is there any elegant and simple way to do this in jQuery?

Answer 1

In the case you should use for loop in javascript instead of using jQuery. See way 3 in http://net.tutsplus.com/tutorials/javascript-ajax/10-ways-to-instantly-increase-your-jquery-performance/

UPDATED: jQuery is written in javascript and it can not be faster than another code written also in javascript. jQuery is very good if you work with the DOM, but doesn’t really help if you’re working with simple javascript arrays or objects.

The code you’re looking for can be something like this:

for (var i=0, l = ar.length; i<l; i++) {
    if (ar[i].ID === specificID) {
        // i is the index. You can use it here directly or make a break
        // and use i after the loop (variables in javascript declared
        // in a block can be used anywhere in the same function)
        break;
    }
}
if (i<l) {
    // i is the index
}

Important that you should hold some simple javascript rules: Always declare local variables (don’t forget var before variable declaration) and cache any properties or indexes that you use more than one time in a local variable (like ar.length above). (See for example http://wiki.forum.nokia.com/index.php/JavaScript_Performance_Best_Practices)