经常使用的js代码小结

在项目中经常会使用到一些小的js代码段，有些用法有时候自己有点犹豫会查API，有些是要我们自己手动写几个demo来搞清楚的，下面是我经常 在工作中使用到的demo。

关于数组的：

1，查询数组中重复的元素，以及重复的次数

var ary = ["1", "33", "22", "1", "1", "22", "22", "33", "22", ‘44‘];
        var res = [];
        ary.sort();
        console.log(ary);
        for (var i = 0; i < ary.length;) {

            var count = 0;
            for (var j = i; j < ary.length; j++) {

                if (ary[i] == ary[j]) {
                    count++;
                }

            }
            if (count > 1){
                res.push([ary[i], count]);
            }
            i += count;

        }
        //res 二维数维中保存了 值和值的重复数
        for (var i = 0; i < res.length; i++) {
            console.log("值:" + res[i][0] + "           重复次数:" + res[i][1] + "<br/>");
        }

2，数组中sort()方法的使用：

demo1：

var objectList2 = new Array();
        function WorkMate(name,age){
            this.name=name;
            var _age=age;
            this.age=function(){
                if(!arguments)
                {
                    _age=arguments[0];}
                else
                {
                    return _age;}
            }

        }
        objectList2.push(new WorkMate(‘jack‘,20));
        objectList2.push(new WorkMate(‘tony‘,25));
        objectList2.push(new WorkMate(‘stone‘,26));
        objectList2.push(new WorkMate(‘mandy‘,23));
        //按年龄从小到大排序
        objectList2.sort(function(a,b){
            return a.age()-b.age();
        });
        for(var i=0;i<objectList2.length;i++){
            document.writeln(‘<br />age:‘+objectList2[i].age()+‘ name:‘+objectList2[i].name);
        }

demo2:

var arrDemo = new Array();

 arrDemo[0] = 10;
 arrDemo[1] = 50;
 arrDemo[2] = 51;
 arrDemo[3] = 100;

 arrDemo.sort(); //调用sort方法后，数组本身会被改变，即影响原数组

 alert(arrDemo);//10,100,50,51 默认情况下sort方法是按ascii字母顺序排序的，而非我们认为是按数字大小排序

 arrDemo.sort(function(a,b){return a>b?1:-1});//从小到大排序

 alert(arrDemo);//10,50,51,100

 arrDemo.sort(function(a,b){return a<b?1:-1});//从大到小排序

 alert(arrDemo);//100,51,50,10

结论:

（1）.数组调用sort方法后，会影响本身(而非生成新数组)

（2）.sort()方法默认是按字符来排序的，所以在对数字型数组排序时，不可想当然的以为会按数字大小排序！

（3）.要改变默认的sort行为(即按字符排序)，可以自行指定排序规则函数(如本例所示)

3、数组的indexOf与splice

function testIndexOfAndSplice() {
        var arr1 = [1, 2, 3, 4, 5];
        var index = arr1.indexOf(5);

        var arr = arr1.splice(index,1);
        console.log(arr1);
        console.log(arr);
    }

4、数组中的concat

function testConcat(){
        var arr1 = [1,2,3,4,5];
        var arr2 = [‘lw‘,‘Jason‘,‘tx‘];
        var arr = arr1.concat(arr2);
        console.log(arr);
    }

关于Date：

function testDate() {
        /*var time1 = "1995-11-17";
        var date1 = new Date(time1);
        var date2 = new Date(1995, 11, 20);
        var difference = date1 - date2;
        console.log(difference);
        console.log( parseInt((difference / (((24 * 60) * 60) * 1000))));*/
        var time = new Date();
        time.setHours(19);
        time.setMinutes(20);
        var difference = time - new Date();
        console.log(difference);
        console.log( parseInt((difference / (((24 * 60) * 60) * 1000))));
        console.log(time.getTime() - new Date().getTime());
    }

关于正则表达式：

var target = ‘icon_skill‘;
        var target1 = ‘icon_wrong‘;
        var postfix= ‘_png‘;
        var str = ‘icon_skill_haha_nono_fafa_png‘;
        var reg = new RegExp(‘^‘+target+‘[a-zA-Z\\_]*‘+postfix+‘$‘);
        var reg1 = new RegExp(‘^‘+target1+‘[a-zA-Z\\_]*‘+postfix+‘$‘);
        var res = reg.exec(str);
        console.log(res[0]); //icon_skill_haha_nono_fafa_png

        res = reg1.exec(str);
        console.log(res); //null

关于JSON

1、stringify

function testStringify(){
        var arr1 = [1,2,3,4,5];
        var arr2 = [‘lw‘,‘Jason‘,‘tx‘];
        var name = "Jason Li";
        var obj = {};
        obj.arr1 = arr1;
        obj.arr2 = arr2;
        obj.name = name;

        var lw = {};
        lw.name = "lw";
        lw.report = JSON.stringify(obj);
        console.log(obj);
        console.log("EEEE");
        console.log(JSON.stringify(lw));     //    {"name":"lw","report":"{\"arr1\":[1,2,3,4,5],\"arr2\":[\"lw\",\"Jason\",\"tx\"],\"name\":\"Jason Li\"}"}
    }

2、parse

function testParse(){

        var str = "{\"result\":\"defender\",\"BATTLE_START\":[{\"content\":[{\"value\":{\"changeModel\":118},\"target\":\"3165150378984059\"}],\"skill\":\"model1\",\"owner\":\"3165150378984059\"},{\"content\":[{\"value\":{\"changeModel\":118},\"target\":\"3164944220554938\"}],\"skill\":\"model1\",\"owner\":\"3164944220554938\"}],\"type\":\"ARENA\"}";
        var strObj = JSON.parse(str);
        console.log(strObj);
        console.log("EEEE");
        //console.log(JSON.parse(strObj));
    }