javascript - jQuery: Index of element in array where predicate

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

See [`Array.filter`][1] to filter an array with a callback function. Each object in the array will be passed to the callback function one by one. The callback function must return `true` if the value is to be included, or false if not.

    var matchingIDs = objects.filter(function(o) {
        return o.ID == searchTerm;
    });

All objects having the ID as searchTerm will be returned as an array to matchingIDs. Get the matching element from the first index (assuming ID is unique and there's only gonna be one)

    matchingIDs[0];

  [1]: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/filter

Update:

Checkout findIndex from ECMAScript 6.

items.findIndex(function(item) { item.property == valueToSearch; });

Since findIndex isn't available on most browsers yet, you could backfill it using this implementation:

if (!Array.prototype.findIndex) {
  Array.prototype.findIndex = function(predicate) {
    if (this == null) {
      throw new TypeError('Array.prototype.findIndex called on null or undefined');
    }
    if (typeof predicate !== 'function') {
      throw new TypeError('predicate must be a function');
    }
    var list = Object(this);
    var length = list.length >>> 0;
    var thisArg = arguments[1];
    var value;

    for (var i = 0; i < length; i++) {
      value = list[i];
      if (predicate.call(thisArg, value, i, list)) {
        return i;
      }
    }
    return -1;
  };
}