为什么将名为value的变量声明为对象会返回Firefox中的函数类型

Question

I have used var values = {}; in a JavaScript file. However when I test my application on Firefox typeof(values) returns function instead of object. This can easily be tested within Firefox console window. As this variable has been used many times in my application; changing it's name may not be a feasible solution. My questions are:

1. Is there a way to force this variable name as an object?
2. What other variable names should i be concerned in order to avoid this problem?

Answer 1

The problem is your assignment tries to change the read-only property window.values which is a function, a console utility.

You don't have such problem if you do it in an inner scope:

(function(){ var values = {}; console.log(typeof values) })()

The difference between Chrome and Firefox is that Chrome doesn't define this property as read-only.

Answer 2

That's just an artifact of the Firefox console, it doesn't affect your real code. If you use typeof values in your actual script code, you'll see that it's undefined (or object if you create it as shown in your question).

Firefox's console provides values as a means of seeing the values of an object:

>> values({foo: "bar"})
-> Array [ "bar" ]

There are other functions available in the Firefox console; they're documented here .

Chrome / Chromium has a bunch of them as well (including values ), documented here .

Is there a way to force this variable name as an object?

In real script code, not the console, there's no problem using values . However, I suggest avoiding creating globals, since the global namespace is very crowded.

What other variable names should i be concerned in order to avoid this problem?

name and title are common ones people trip over. This is another reason not to use global variables. Instead, put your code in a scoping function:

(function() {
    // Your code here
})();

Answer 3

Because by doing so in firefox, you're trying to override/re-assign the global read-only window object values which type is function

window.values // its a function

Chrome however doesnt treat values as a read-only object

In order to make it works as you wish in Firefox, you need to place it inside a function

function test() {
  var values = {};
  console.log(typeof values); // typeof: object
}