Join two normalized arrays using a join table, returning a copy of the first array containing a property with an array of mapped elements of arr2

joinArrays.js

/**
 * Join two normalized arrays using a join table, returning a copy of
 * the first array containing a property with an array of mapped
 * elements of arr2
 *
 * @see normalizeArrayId
 *
 * @param arr1 Normalized array 1
 * @param arr2 Normalized array 2
 * @param arrJoin Array with the joins
 * @param key1 Key of the property in arrJoin that maps to arr1
 * @param key2 Key of the property in arrJoin that maps to arr2
 * @param newProperty New property on the returned array that will contain mapped values from arr2
 * @return {Array}
 */
function joinArrays(arr1, arr2, arrJoin, key1, key2, newProperty){
    var total = arrJoin.length,
        total1 = arr1.length,
        ret = {},
        i;

    for(i=0; i<total1; i++){
        if(typeof(arr1[i]) === 'undefined') continue;
        ret[arr1[i].Id] = angular.copy(arr1[i]);
        ret[arr1[i].Id][newProperty] = [];
    }

    for(i=1; i<total; i++){
        ret[arrJoin[i][key1]][newProperty].push(arr2[arrJoin[i][key2]]);
    }
    return ret;
};