1、对象遍历（for-in）：

var obj = {
	'0':'a',
	'1':'b',
	'2':'c'
};

// i遍历为key
for(var i in obj) {
     console.log(i,":",obj[i]);
}

2、数组遍历（for-in）

var arr=["张三","李四","王五","赵六"];

// i遍历为下标
for (var i in arr){
    console.log(i,":",arr[i]);
}

3、数组遍历（for-of）

var arr=["张三","李四","王五","赵六"];

// value遍历为元素
for (var value of arr){
    console.log(value);
}