How do I check for undefined values in IE8?

Question

I have this in my javascript:

console.log(filters);
console.log('----');
console.log(filters.max_price);

In Chrome, it shows this. This is the expected behavior.

Object {max_price: undefined, sort_by: undefined, distance: undefined, start: undefined, num: undefined}
----
undefined

In IE8, the log shows this:

LOG: Object Object
----
LOG: String

Why does IE8 think it is a string? I need to know if it's undefined.

I have lots of code that sets default values.

if(typeof filters.max_price == undefined){ //I use this technique a lot! 
    filter.max_price = 2000; 
}

How can I check for undefine-ds in IE8? Should I do this? This seems to work (yay...), but it seems cheap and hacky.

if(!filters.max_price || typeof filters.max_price == 'undefined'){

Is there a simple way I can do this with underscore?

Do you mean `undefined` as in "declared but not defined", or `undefined` as in "not declared nor defined"; two different things... — elclanrs, Apr 26 '13 at 08:07
http://stackoverflow.com/questions/690251/what-happened-to-console-log-in-ie8 — Jørgen R, Apr 26 '13 at 08:07
@jurgemaister yea I know... but that has nothing to do with the question — TIMEX, Apr 26 '13 at 08:09
IE8's `console` isn't really that good. It's better in later IE versions, but if you need to work in IE8, you could try using [Firebug Lite](https://getfirebug.com/firebuglite) instead. It'll give you more functionality for inspecting you JS data, etc. — Spudley, Apr 26 '13 at 08:43

score 5 · Accepted Answer · answered Apr 26 '13 at 08:09

5

You can use this approach, but it would not reduce your code a lot:

filters.max_price = filters.max_price || 2000;

This, however, would overwrite the value if it's 0. The best approach remains:

if(typeof filters.max_price === 'undefined'){
    // init default
}

answered Apr 26 '13 at 08:09

Konstantin Dinev

Is the === better than my current version of ==? Will triple === work with IE8? – TIMEX Apr 26 '13 at 08:10
@TIMEX Triple also compares types and the type of undefined is "undefined" – Konstantin Dinev Apr 26 '13 at 08:11
It doesn't work with IE8. if(typeof filters.max_price === 'undefined'){ ....IE8 does not catch it. – TIMEX Apr 26 '13 at 08:12
>> filters.max_price = undefined >> typeof filters.max_price === "undefined" true – Konstantin Dinev Apr 26 '13 at 08:19
`undefined` is a _falsy_ statement therefore it should evaluate to false in a conditional statement. Checking for its type is a bad way of doing things because of browser inconsistencies. `if(!filters.max_price)` is all you need. – Andrei Nemes Apr 26 '13 at 08:20
@AndreiNemes And that returns true when max_price = 0 – Konstantin Dinev Apr 26 '13 at 08:21
No it doesn't. 0 is also falsy. – Andrei Nemes Apr 26 '13 at 08:22
@AndreiNemes yes so not-ing it is true is what I'm saying. The person wants to check for undefined and doesn't want to overwrite values like 0. – Konstantin Dinev Apr 26 '13 at 08:24
Then simply check if it's a number `if(isNaN(filters.max_price))` – Andrei Nemes Apr 26 '13 at 08:36
1

Max price is a string? What's the value range then? – Andrei Nemes Apr 26 '13 at 08:39

Andrei Nemes · Answer 2 · 2013-04-26T08:43:38.990

0

You can use a guard operator to set a default value:

filters.max_price = filters.max_price || 2000;

To check if the value is a number (which I supposed a price is), you can use

if(isNaN(filters.max_price)) {
    //enter code here
}

This will also filter out undefined as not a number.

edited Apr 26 '13 at 08:43

answered Apr 26 '13 at 08:09

Andrei Nemes

2 Answers2