Array safe replace for when Angular isn't kind

arraySafeReplace.ts

declare module _ {
    interface LoDashStatic {
        arraySafeReplace: (existingArray: any[], newArray: any[]) => any[];
    }
}

_.mixin({ "arraySafeReplace": (existingArray: any[], newArray: any[]) => {
    if (existingArray) {
        existingArray.length = 0;
    } else {
        existingArray = [];
    }

    Array.prototype.push.apply(existingArray, newArray);

    return existingArray;
}});