function forEach(obj, fn){
    var key
    if(obj instanceof Array){
        obj.forEach(function(item, index){
            fn(index, item)
        })
    }else{
        for(key in obj){
            fn(key, obj[key])
        }
    }
}
var arr = [1,2,3]
forEach(arr, function(index, item){
    console.log(index, item)
})
var obj = {x:100,y:200}
forEach(obj, function(key, value){
    console.log(key, value)
})

相关资料

能遍历对象和数组的forEach函数