js实践问题收集日记

1.js的sort(）方法

使用方法：

(1).ArrObject.sort();

若sort()函数没有参数，则按数组中的字母顺序排序，即字符编码顺序排序，因此如果要进行排序，应先将数组元素转变为字符串再进行排序。

sort（）函数默认升序排序。

(2).ArrObject.sort(sortby);

sort函数也可以接收参数，但参数sortby必须是一个函数。

var  arr = [1,2,3];

调用sort()函数对arr进行排序

arr.sort(sortby);

function sortby(a,b){
     //升序排序
       return a - b;
     //降序  
      // return b - a;          
} 

(3).sort()函数按某一属性对json数组排序

json数组

var imgData = {"data":[{"src":"26.jpg","author":"太郎","date":"03-12","num":123},{"src":"27.jpg","author":"xiaotaio","date":"03-13","num":1563},{"src":"29.jpg","author":"筱筱","date":"03-12","num":5663},{"src":"83.jpg","author":"小哈就","date":"03-12","num":454},{"src":"30.jpg","author":"成本撒阿萨","date":"03-12","num":765},{"src":"38.jpg","author":"石帆胜丰","date":"03-12","num":5643},{"src":"50.jpg","author":"大范甘迪","date":"03-12","num":655}]} 
console.log(imgData.data.sort(numDown('num')));

sortNum函数

function sortNum(property){
            return    function numDown(arr,brr){
                var value1 = arr[property];
                var value2 = brr[property];
                return value2 - value1;

            }
        }

 2.js中变量加var和不加var的区别

https://blog.csdn.net/hero_xsx/article/details/81562055

3.作用域和作用域链

4.闭包