JavaScript variable scope in Google Chrome

Question

I've got the following code :

<!DOCTYPE html>
<html>

<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<title>Untitled 1</title>
</head>

<body>

<p id="p"></p>

<script>

var top = 9;
( function () {  top += 1;  document.getElementById( "p" ).innerHTML = top;  } )()

</script>

</body>

</html>

It works fine in Internet Explorer ( prints 10 ), but in Google Chrome it prints [object Window]. But if i change it like this:

( function () {  var top = 9; top += 1; document.getElementById( "p" ).innerHTML = top; } )()

it works in Chrome fine too. The only change is that the variable is now local. Does it mean that in Chrome i can't access global variables? Whatever i do i can't get the right result..

Don't use global variables.

user1106925
– user1106925

2014-11-07 21:17:02 +00:00
Commented Nov 7, 2014 at 21:17 — user1106925
– user1106925, Commented Nov 7, 2014 at 21:17
window.top is an object

Ryan
– Ryan

2014-11-07 21:17:09 +00:00
Commented Nov 7, 2014 at 21:17 — Ryan
– Ryan, Commented Nov 7, 2014 at 21:17

Sterling Archer · Accepted Answer · 2014-11-07 21:16:22Z

2

Change your variable name, as it's conflicting with the Window.top global object. See the MDN doc page

answered Nov 7, 2014 at 21:16

Sterling Archer

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6 Comments

Sterling Archer Over a year ago

I had the same issue with a variable named status. Learned the hard way lol

Alex Oswald Over a year ago

These name conflicts seem really unconvinient. That's the big disadvatage of javascript and other such languages i think.. In Java language there are no such problems for example

Sterling Archer Over a year ago

Of course there are. Every try to assign a reserved word in Java?

Alex Oswald Over a year ago

That's just reserved words :) There are little bit of them and you can remember almost all of them since they're commonly used. But in other languages there are many such "hidden" words, which you don't know about. And it's just unconvinient to have one big global namespace

VLAZ Over a year ago

@AlexOswald and that's precisely why your second function works - it's because it is NOT in the global namespace. There are two namespaces - global and function, it's advisable to not use global for the precise reason you saw.

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