Given an array of objects that have an Id, return an array where the Id is the key

normalizeArrayId.js

/**
 * Given an array of objects that have an Id, return an array where the Id is the key
 * @param arr Array to normalize
 * @param key [Optional] Object key to use, defaults to Id
 * @returns {Array} Normalized array
 */
function normalizeArrayId(arr, key){
    var total = arr.length,
        index = key || 'Id',
        ret = [];
    for(var i=0; i<total; i++){
        ret[arr[i][index]] = arr[i];
    }
    return ret;
};