1、js,jquery for循环第一种方法：var arr=['baidu','baiduyun','baidujingyan','baidushiping']for (i in arr){console.log(arr[i]);} #遍历arr数组的索引，将arr的元素取出输出结果：baidubaiduyunbaidujingyanbaidushiping
3、js,jquery for循环第二种方法：var arr=['baidu','baiduyun','baidujingyan','baidushiping'];arr.map(function(val,index,arrnow){console.log(val,index,arrnow)})#以上方法map中的function实际有三个参数currentValue ->数组中遍历到的元素index -> 数组中遍历到的元素的索引array -> map方法被调用的数组，也就是arr本身以上输出结果：baidu 0 (4) ["baidu", "baiduyun", "baidujingyan", "baidushiping"]baiduyun 1 (4) ["baidu", "baiduyun", "baidujingyan", "baidushiping"]baidujingyan 2 (4) ["baidu", "baiduyun", "baidujingyan", "baidushiping"]baidushiping 3 (4) ["baidu", "baiduyun", "baidujingyan", "baidushiping"]
4、以上介绍了常用的三种js,jquery遍历数组的方法，那么如果遍历对象呢var obj={'baidu':'百度','baiduyun':'百度云','baidujingyan':'百度经验','baidushiping':'百度视频'};for (keys in obj){console.log(keys+':',obj[keys])}baidu: 百度baiduyun: 百度云baidujingyan: 百度经验baidushiping: 百度视频这时候forEach和map方法就不可以使用了，如果使用则会报错：Uncaught TypeError: obj.forEach is not a function at <anonymous>:1:5
