A list of helpers for handling copying, clearing arrays quickly and easily.

ArrayHelpers.js

/* Array.isArray polyfill - taken from https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray */
if (!Array.isArray) {
  Array.isArray = function (arg) {
    return Object.prototype.toString.call(arg) === '[object Array]'
  }
}

function ArrayHelpers() {

}

/**
 * copies all entries from array given as the second argument into the array 
 * given as first argument. 
 * 
 * Please Note: This will keep all the entries already existing!
 *              If you do not wish this behavior, use "fastFillArray"
 * 
 * @param  {Array} arrayToFill              the array to copy entries into
 * @param  {Array} arrayWithEntriesToFillIn the array to copy over
 */
ArrayHelpers.copyBetweenArrays = function copyBetweenArrays(arrayToFill, arrayWithEntriesToFillIn) {
    if (ArrayHelpers.isArrayLike(arrayToFill) && ArrayHelpers.isArrayLike(arrayWithEntriesToFillIn)) {
        Array.prototype.push.apply(arrayToFill, arrayWithEntriesToFillIn);
    }

    return arrayToFill;
};

ArrayHelpers.isArrayLike = function isArrayLike(subject) {
    return !!(subject && (Array.isArray(subject)) && ('push' in subject));
};

/**
 * clears the first argument's array and fills all entries from array given as
 * the second argument.
 *
 * Please Note: This will remove all entries from the first argument array!
 * 
 * @param  {Array} arrayToFill              the array to clear and fill into
 * @param  {Array} arrayWithEntriesToFillIn the array to copy over
 */
ArrayHelpers.fastFillArray = function fastFillArray(arrayToFill, arrayWithEntriesToFillIn) {
    if (ArrayHelpers.isArrayLike(arrayToFill) && ArrayHelpers.isArrayLike(arrayWithEntriesToFillIn)) {
        arrayToFill.length = 0;
        ArrayHelpers.copyBetweenArrays(arrayToFill, arrayWithEntriesToFillIn);
    }

    return arrayToFill;
}

/**
 * clears the first argument's array. This will remove all entries from it.
 * 
 * @param  {Array} array                    the array to clear
 */
ArrayHelpers.clearArray = function clearArray(array) {
    if (ArrayHelpers.isArrayLike(array)) {
        array.length = 0;
    }
}