JS parseInt() issue

Question

I know I might be doing something wrong. Can anyone please point out why I'm getting top as object??

$(document).ready(function(){
    topwithpx='0px';
    alert(topwithpx);
    topstr=topwithpx.substr(0,topwithpx.length-2);
    alert(topstr);
    top=parseInt(topstr);
    alert(top);
});

http://jsfiddle.net/kjMs9/

Thanks all: 'top' is reserved keyword (Window.top). My bad. Accepting first ans. +1 to all for quick ans.

Can you include your problem in this question? Otherwise it's going to get closed pretty quickly. — Mike Robinson
– Mike Robinson, Commented Aug 23, 2012 at 14:12
From your fiddle, I get top's value as 0. What is your question? — Nivas
– Nivas, Commented Aug 23, 2012 at 14:14
May I also suggest you look at JsLint jslint.com it will point out issues like this and others. — Mark Broadhurst
– Mark Broadhurst, Commented Aug 23, 2012 at 14:16
Thanks for edit mike. @Nivas: Really? In my chrome, I'm getting [object Window] as third popup. Please try in chrome. — Kapil Sharma
– Kapil Sharma, Commented Aug 23, 2012 at 14:16
Unrelated, but don't forget your radix parameter in parseInt() - you might end up with some unexpected results if you don't. — Daniel Attfield
– Daniel Attfield, Commented Aug 23, 2012 at 14:21

raina77ow · Accepted Answer · 2012-08-23 14:13:25Z

9

Because it's essentially window.top, which is Window object. Use var top instead to prevent mixing local variable with global (= properties of window object) ones.

In fact, make var-ing your function variables something of a common routine - to prevent getting similar gotchas in the future. )

answered Aug 23, 2012 at 14:13

raina77ow

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4 Comments

jbabey Over a year ago

shadowing a global variable is not a good suggestion, you should never name a variable top.

Kapil Sharma Over a year ago

Thanks for any. My bad. Thats correct. +1 for quick ans to every one.

raina77ow Over a year ago

@jbabey Because of what? When JS parser will try to determine the variable's value, it always starts from the lowest (local) scope. I do agree that it's not a good idea to use top instead of window.top, though, if you address that property.

jbabey Over a year ago

@raina77ow shadowing is a bad practice, but this is matter of opinion.

Curtis · Accepted Answer · 2012-08-23 14:14:02Z

4

You don't need to use substr to remove the px. parseInt will do this for you:

topwithpx='0px';
var top = parseInt(topwithpx);
alert(top);  //alerts "0"

http://jsfiddle.net/kjMs9/3/

answered Aug 23, 2012 at 14:14

Curtis

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Comments

Quentin · Accepted Answer · 2012-08-23 14:13:45Z

3

window.top is part of DOM 0 and can't be assigned a Number.

Avoid using global variables. Scope them with var

$(document).ready(function(){
    var topwithpx, topstr, top;
    topwithpx='0px';
    alert(topwithpx);
    topstr=topwithpx.substr(0,topwithpx.length-2);
    alert(topstr);
    top=parseInt(topstr);
    alert(top);
});

answered Aug 23, 2012 at 14:13

Quentin

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2 Comments

tomsmeding Over a year ago

This is about what I was going to post :) See this link please.

Kapil Sharma Over a year ago

Thanks for any. My bad. Thats correct. +1 for quick ans to every one.

jbabey · Accepted Answer · 2012-08-23 14:13:51Z

3

top is a default property of the window object (MDN). Name your variable something else.

answered Aug 23, 2012 at 14:13

jbabey

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2 Comments

jbabey Over a year ago

@jAndy it's a reference to a window, not the current window. and yes, it is a property of the current window object.

jAndy Over a year ago

I'm a little confused. top in window returns true in FF, but Object.getOwnPropertyNames( window ); doesn't show that property at all. Chrome on the other side, gets the top and self properties correctly with getOwnPropertyNames

Explosion Pills · Accepted Answer · 2012-08-23 14:32:45Z

2

top is a read-only property of the window (at least for Mozilla, but probably all the other big browsers as well).

Just change top to something else like topInt. Also, use var to declare variables (e.g. var topInt = parseInt(...). If you don't use var, then the window property is used by default, hence the read-only behavior.

By the way, it would be a bit nicer to use console.log instead of alert

edited Aug 23, 2012 at 14:32

answered Aug 23, 2012 at 14:14

Explosion Pills

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1 Comment

Mark Broadhurst Over a year ago

Top is not a reserved word developer.mozilla.org/en-US/docs/JavaScript/Reference/…

Uchenna Nwanyanwu · Accepted Answer · 2012-08-23 14:15:11Z

1

top is a javascript window property. You can use top as a variable by doing this

var top = ...

answered Aug 23, 2012 at 14:15

Uchenna Nwanyanwu

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2 Comments

jbabey Over a year ago

top is not a reserved word.

tomsmeding Over a year ago

@jbabey but it is a standard window property which you can't use for something else than reading, see this page.

Anant Dabhi · Accepted Answer · 2012-08-23 14:18:14Z

1

$(document).ready(function(){
    topwithpx='0px';
    alert(topwithpx);
    topstr=topwithpx.substr(0,topwithpx.length-2);
    alert(topstr);
   var top=parseInt(topstr);
    alert(top);
});

you missing delcaration of variable

answered Aug 23, 2012 at 14:18

Anant Dabhi

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