lib/Ext/util/Collection.js
function(item) {
        if (this.dirtyIndices) {
            this.updateIndices();
        }

        var index = item ? this.indices[this.getKey(item)] : -1;
        return (index === undefined) ? -1 : index;
    }
function(item) {
        if (this.dirtyIndices) {
            this.updateIndices();
        }

        var index = item ? this.indices[this.getKey(item)] : -1;
        return (index === undefined) ? -1 : index;
    }
Returns index within the collection of the passed Object.
@param {Object} item The item to find the index of.
@return {Number} Index of the item. Returns -1 if not found.