ampersand-collection-underscore-mixin/ampersand-collection-underscore-mixin.js

var _ = require('underscore');
var slice = [].slice;
var mixins = {};


// Underscore methods that we want to implement on the Collection.
var methods = ['forEach', 'each', 'map', 'collect', 'reduce', 'foldl',
    'inject', 'reduceRight', 'foldr', 'find', 'detect', 'filter', 'select',
    'reject', 'every', 'all', 'some', 'any', 'include', 'contains', 'invoke',
    'max', 'min', 'toArray', 'size', 'first', 'head', 'take', 'initial', 'rest',
    'tail', 'drop', 'last', 'without', 'difference', 'indexOf', 'shuffle',
    'lastIndexOf', 'isEmpty', 'chain', 'sample', 'partition'
];

// Mix in each Underscore method as a proxy to `Collection#models`.
_.each(methods, function (method) {
    if (!_[method]) return;
    mixins[method] = function () {
        var args = slice.call(arguments);
        args.unshift(this.models);
        return _[method].apply(_, args);
    };
});

// Underscore methods that take a property name as an argument.
var attributeMethods = ['groupBy', 'countBy', 'sortBy', 'indexBy'];

// Use attributes instead of properties.
_.each(attributeMethods, function (method) {
    if (!_[method]) return;
    mixins[method] = function (value, context) {
        var iterator = _.isFunction(value) ? value : function (model) {
            return model.get ? model.get(value) : model[value];
        };
        return _[method](this.models, iterator, context);
    };
});

// Return models with matching attributes. Useful for simple cases of
// `filter`.
mixins.where = function (attrs, first) {
    if (_.isEmpty(attrs)) return first ? void 0 : [];
    return this[first ? 'find' : 'filter'](function (model) {
        var value;
        for (var key in attrs) {
            value = model.get ? model.get(key) : model[key];
            if (attrs[key] !== value) return false;
        }
        return true;
    });
};

// Return the first model with matching attributes. Useful for simple cases
// of `find`.
mixins.findWhere = function (attrs) {
    return this.where(attrs, true);
};

// Plucks an attribute from each model in the collection.
mixins.pluck = function (attr) {
    return _.invoke(this.models, 'get', attr);
};

module.exports = mixins;