数组里面获取键名和键值

https://www.cnblogs.com/xxmb/archive/2013/11/19/3431118.html

https://www.cnblogs.com/platycoden/p/5204362.html

对于json对象:

var arr={'a':1,'b':2,'c':3};
for (var k in arr){  
alert(k+' : '+arr[k]);  
}

对于数组对象:

var arr = [
        [10,'zhangsan','male'],
        [11,'lisi','female'],
        [12,'wangwu','male']
    ];
for (var i in arr){
    for(var j in arr[i]){
        document.write(arr[i][j]);
    }
    document.write('<br>');
}