在javascript中我们通常用的for，for in方法总感觉没什么区别，但是在一次的学习的过程中我发现了for与for in还真有点区别。接下来让我们简单的区分一下：
首先先看一下for的语法的结构以及他的写法
for（初始值，判断条件，步长值）{
}；
for（i=0;i<10;i++）{
console.log(i) //0 1 2 3 4 5 6 7 8 9
};
for in是用来遍历来用的
data={
x:["一月","二月","三月","四月","五月","六月"],
y:["0","100","200","300","400","500","600","700","800","900","1000"],
val:["300","210","120","560","800","660"],
col:["red","green","blue","skyblue","orange","pink"]
}
for（var i in data.x/y/val/col）{
console.log(data.x[i])//会打印出data对象里x的每一项，["一月","二月","三月","四月","五月","六月"]
}
var data = {//data只是个变量名
age:20,
name:"小李子",
xingbie:"男"
}
for(var i in data){
console.log(i);// 输出的是 k值：age name sex
console.log(wq[attr]);//属性相对应的value值 20 小李子 男
}
两者一对比就大致可以看出for in遍历对象是最适合了，如果用for的话，对象里面的k值和value值只好无能为力，那就只能用for in。如果只是普通的数组，用for最适合；那如果for in遍历普通数组话，他会自带length属性，到后面会报错，所以for in不适合循环遍历普通数组。
