Javascript - functional functions

Javascript - Functional functions

	function arrayEach(arr, callback) {
		for (var i = 0; i < arr.length; i++) {
			callback(arr[i], i);
		}
	}

	function arraySelect(arr, callback) {
		var newArr = [];

		for (var i = 0; i < arr.length; i++) {
			if( callback(arr[i], i) ) {
				newArr.push(arr[i]);
			}
		}

		return newArr;
	}

	function arraySelectFirst(arr, callback) {
		for (var i = 0; i < arr.length; i++) {
			if( callback(arr[i], i) ) {
				return arr[i];
			}
		}
		return null;
	}

	function arrayMap(arr, callback) {
		var newArr = [];

		for (var i = 0; i < arr.length; i++) {
			newArr.push( callback(arr[i], i) );
		}

		return newArr;
	}

	function arrayReduce(arr, callback, alt) {
		var total = def(alt, 0);

		for (var i = 0; i < arr.length; i++) {
			total = callback(total, arr[i], i, arr);
		}

		return total;
	}

	function objectEach(obj, callback) {
		for (var key in obj) {
			if( obj.hasOwnProperty(key) ) {
				callback(obj[key], key);
			}
		}
	}

	function objectMap(obj, callback) {
		var newObj = {};

		objectEach(obj, function(value, key) {
			newObj[key] = callback(value, key);
		});

		return newObj;
	}

	function objectSelect(obj, callback) {
		var newObj = {};

		objectEach(obj, function(value, key) {
			if( callback(value, key) ) {
				newObj[key] = value;
			}
		});

		return newObj;
	}

	function objectReduce(obj, callback, alt) {
		var total = def(alt, 0);

		objectEach(obj, function(key, value) {
			total = callback(total, value, key, obj);
		});

		return total;
	}

	function each(obj, callback) {
		if( isObject(obj) ) {
			objectEach(obj, callback);
		} else if( isArray(obj) ) {
			arrayEach(obj, callback);
		} else {
			arrayEach([ obj ], callback);
		}
	}

	function newObj(obj) {
		if( isObject(obj) ) {
			return {};
		} else {
			return [];
		}
	}

	function appendObj(newObj, value, key) {
		if( isObject(newObj) ) {
			newObj[key] = value;
		} else if( isArray(newObj) ) {
			newObj.push(value);
		} else {
			newObj = [ value ];
		}
	}

	function map(obj, callback) {
		var n = newObj(obj);

		each(obj, function(value, key) {
			appendObj(n, callback(value, key), key);
		});

		return n;
	}

	function select(obj, callback) {
		var n = newObj(obj);

		each(obj, function(value, key) {
			if( callback(value, key) ) {
				appendObj(n, value, key);
			}
		});

		return n;
	}

	function reduce(obj, callback, alt) {
		var total = def(alt, 0);

		each(obj, function(value, key) {
			total = callback(total, value, key, obj);
		});

		return total;
	}