underscorish.js

define(function () {

    var _ = { };

    (function() {

each

_.each(collection, iterator)

Public: Iterates over elements of a collection, executing the callback for each element. The callback is invoked with three arguments: (value, index|key, collection).

collection - (Array|Object): The collection to iterate over.

iterator - (Function): The function called per iteration.

Returns nothing.

        _.each = function(collection, iterator) {
            if ( collection === undefined )
                return;
            else if (collection.length) {
                for ( var i = 0; i < collection.length; i++)
                    iterator(collection[i], i, collection);
            } else {
                for (var key in collection) {
                    iterator(collection[key], key, collection);
                }
            }
        };

map

_.map(collection, iterator)

Public: Creates an array of values by running each element in the collection through the callback. The callback is invoked with three arguments: (value, index|key, collection)..

collection - (Array|Object): The collection to iterate over.

iterator - (Function): The function called per iteration.

Returns (Array): Returns a new array of the results of each callback execution.

        _.map = function(collection, iterator) {
            var mapped = [];
            _.each(array, function(item){
                mapped.push(iterator(item));
            })
            return mapped;
        };

filter

_.filter(collection, iterator)

Public: terates over elements of a collection, returning an array of all elements the callback returns truthy for. The callback is invoked with three arguments: (value, index|key, collection).

collection - (Array|Oject): The collection to iterate over.

iterator - (Function): The function called per iteration.

Returns (Array): Returns a new array of elements that passed the callback check.

        _.filter = function(collection, iterator) {
            var filtered = [];
            _.each(array, function(item){
                if(iterator(item))
                    filtered.push(item);
            })
            return filtered;
        };

reduce

_.reduce(collection, iterator, initialValue)

Public: Reduces a collection to a value which is the accumulated result of running each element in the collection through the callback, where each successive callback execution consumes the return value of the previous execution. If not provided initialValuedfault to 0. The callback is invoked with two arguments; (initialValue, value).

collection - (Array|Object): The collection to iterate over.

iterator - (Function): The function called per iteration.

initialValue - (*): Initial value of the accumulator.

Returns the accumulated value.

        _.reduce = function(collection, iterator, initialValue) {
           initialValue = initialValue || 0;
            _.each(collection, function(value){
               initialValue = iterator(initialValue, value);
            });
           return initialValue;
        };

every

_.every(collection, iterator)

Public: Checks if the given callback returns truthy value for all elements of a collection. The callback is invoked with three arguments; (value, index|key, collection)..

collection - (Array|Object): The collection to iterate over.

iterator - A test function to be called to to filter the array.

Returns (boolean): Returns true if all elements passed the callback check, else false.

        _.every = function(collection, iterator) {
            return _.reduce(collection, function(wasTrue, value){
                if (wasTrue)
                    if(iterator)
                        return iterator(value) ? true : false;
                    else
                        return (value) ? true : false;
                else
                    return false;
            }, true);
        };


    })();
    return _ ;
});