es5

Posted 2021-01-30 tuziling

   var arr1=["上海","北京","广州"];
            var arr2=[12,22, 33,58,32,45,92];
             // 数组.方法(function (item, index) {})
            // 1. forEach  等价 for
            arr1.forEach(function(item,index){
                console.log(item,index);
                //上海 北京 广州
                //0     1    2
            }); 
             // 2. map 映射
            var arrMap=arr2.map(function(item,index){
                return item *2;
            })
            console.log(arrMap,"map");//[24, 44, 66, 116, 64, 90, 184] "map"
            //3.filter 过渡
            var arrFilter=arr2.filter(function(item,index){
                return item >50;
            });
            console.log(arrFilter,"arrFilter");//(2) [58, 92] "arrFilter"
            //4.every 每一个的意思 他会返回ture或者false
            //所有的条件全部满足就返回ture否则返回false
            var flagEvery=arr2.every(function(item,index){
                return item > 30;
            })
            console.log(flagEvery,"every");
            //5.some 每一个的意思 他会返回ture或者false
            //只要有一个条件满足就返回ture否则返回false
            var flagSome=arr2.some(function(item,inde){
                return item>30;
            })
            console.log(flagSome,"some");