underscore

一直想为js写一个数组排序，遍历，字符串操作的综合的大类，不知道尽然有Underscore这么好的东西。

Underscore是与backnone一起的方法库。来见识一下underscore的强大吧。

 _each ：_.each(list, iterator, [context])

list 为数组时 iterator传递三个参数(element, index, list)

list为对象时 iterator传递三个参数(value, key, list)

如果传递了context参数，则把iterator绑定到context对象上。

var someOtherArray = ["name","patrick","d","w"];

_.each([1, 2, 3], function(num) { 
    // In here, "this" refers to the same Array as "someOtherArray"

    alert( this[num] ); // num is the value from the array being iterated
                        //    so this[num] gets the item at the "num" index of
                        //    someOtherArray.
}, someOtherArray);

 

 

var person = {};
person.friends = {
  name1: "kitty",
  name2: "sonny",
  name3: "age",
  name4: "ponny"
};

_.each(['name4', 'name2'], function(name){
  // this refers to the friends object op person
  alert(name+":"+this[name]);
}, person.friends);

这样当遍历一个数据集合只需或个别属性的值，不需要通过if else这样繁琐的判断，对比jquery的$.each()多了context参数。不能代替$(obj).each().

 

 

sortby：uderscore轻松完成多维数组单个字段的（时间，数字，字符）排序

 (function ($) {
        var arry=[{name:"kityy",age:21},
            {name:"sonny",age:3 },
            { name:"bage",age:29},
            {name:"quick",age:33 },
            { name:"funny",age:35 }]
       var sorted= _.sortBy(arry,function(data){ return -data.age})
        for(var i = 0; i < sorted.length; ++i)
            console.log(sorted[i]["name"]+":"+sorted[i]["age"]);
    })(jQuery);

在backbone中使用：

 M = Backbone.Model.extend();
        C = Backbone.Collection.extend({
            model: M
        });
        var c = new C();
        c.add([
            {name:"kityy",age:21},
            {name:"sonny",age:3 },
            { name:"bage",age:29},
            {name:"quick",age:33 },
            { name:"funny",age:35 }
        ]);
        var sorted = c.sortBy(function(m) { return -m.get('age')});
        for(var i = 0; i < sorted.length; ++i)
            console.log(sorted[i].get('name')+":"+sorted[i].get('age'));

 flatten_.flatten(array)将多维数组合并成一位数组，js里用处不大

 

extend: underscore 合并对象，翻译成update对象更形象，backbone依赖这个方法做做原型链的扩展

    var ArrayProto = Array.prototype,
    slice = ArrayProto.slice

    var extend = function (obj) {
        _.each(slice.call(arguments, 1), function (source) {
            if (source) {
                for (var prop in source) {
                    obj[prop] = source[prop];
                }
            }
        });
        return obj;
    };

使用方法

extend(hh,{o:21},{mm:45})