为什么不能为每个对象迭代对象

Question

I am trying to iterate over an object with the forEach array method.

var obj = {"a":1, "b":2, "c":3};
[].forEach.call(obj, function(n, key) {
    console.log(key, n)
})

should Print

a:1

b:2

c:3

This doesn't work as it returns undefined in the debugger even when I artificially add a length property to the obj

obj.length = 3;

How do I make this object array like so i can call array method like foreach on the object. I am aware there are other ways to iterate over an object was just wondering what I was doing wrong in this scenario.

Answer 1

Array.prototype.forEach() will only work on arrays and not on objects. You could use Object.keys() to loop over the object's own enumerable properties:

var obj = {"a":1, "b":2, "c":3};

Object.keys(obj).forEach(function(key) {
    console.log(key, obj[key]);
});