empty jQuery string not empty

Question

Can someone please explain this to me? I am attempting to do something if key != ''

var key = "";
if($('div[title="Keyword"]').text() != '') {
  key = $('div[title="Keyword"]').text().trim(); 
}

//this always alerts
if (key != '') { alert(key); } 

//this never alerts
if (!key) { alert(key); }

alert the value of key before the if and see what is it equal to. If it's not an empty string, then the first `if` will pass. — David G, Oct 04 '12 at 00:15
I set up a jsfiddle at http://jsfiddle.net/SPJPq/ and works as I would expect. Can you reproduce the issue you are seeing there? — Bill, Oct 04 '12 at 00:17
You may have some invisible special character not removed by `trim` — bfavaretto, Oct 04 '12 at 00:17
I don't understand what's asked here. For any non-empty string in `key`, `key != ''` will evaluate to `true`, and `!key` will evaluate to `false`. — raina77ow, Oct 04 '12 at 00:17
How to check input for empty: http://stackoverflow.com/questions/1854556/check-if-inputs-are-empty-using-jquery — Alex, Oct 04 '12 at 00:18
@wroniasty `console.log(key)` says it is empty no matter where I put it. — Jonathan Eckman, Oct 04 '12 at 00:22
@raina77ow Isnt `!key` similar to saying `key != '' || key == undefined` — Jonathan Eckman, Oct 04 '12 at 00:23
@Feature: You should log `key.length`. If it comes up as greater than 1, then log `key.charCodeAt(0)`. — I Hate Lazy, Oct 04 '12 at 00:25
What's actually in the DIV that you're checking? Show us the HTML. — Barmar, Oct 04 '12 at 00:25
@Feature Of course not. `!key` will evaluate to `true` only if `key` is falsy; the only falsy String value is `''` - an empty string. — raina77ow, Oct 04 '12 at 00:30
@user1689607 Good call. `key.length` is 1, `key.charCodeAt(0)` is 8203. I think I can solve this by checking if `key.length > 1` — Jonathan Eckman, Oct 04 '12 at 00:32
@Feature: You should solve it by deleting these characters from your markup. They shouldn't be there. Sometimes they can crop up when you copy and paste code from websites. — I Hate Lazy, Oct 04 '12 at 00:33
How come checking `key.length > 0` (actually; not 1) is better than checking `key !== ''`, is beyond me. — raina77ow, Oct 04 '12 at 00:34
@bfavaretto had it right a long time ago. He should add an answer. — I Hate Lazy, Oct 04 '12 at 00:36

score 1 · Accepted Answer · answered Oct 04 '12 at 00:51

I said in the comments it might be an invisible character not stripped by trim. Well, after your further comments, it's clear that's the case. It's the U+200B Zero-width space character. It probably came from jsfiddle (I'm betting you pasted something from there).

empty jQuery string not empty

1 Answers1