Javascript and Angular undefined variables determination

Question

I'm trying to understand better how to determine if a variable is undefined and I get mixed results, hopfuly someone can make it clearer.

This is the example:

enter image description here

What I expect is none_exisiting_variable to result 'false' for the isDefined check.

Related: [JavaScript check if variable exists (is defined/initialized)](http://stackoverflow.com/questions/5113374/javascript-check-if-variable-exists-is-defined-initialized-which-method-is-b) — Jonathan Lonowski, Jan 09 '15 at 14:24
Hey thanks, I came across this post but wanted to discover if there is an angular way to overcome this — Ben Diamant, Jan 09 '15 at 14:25

Denys Séguret · Answer 1 · 2015-01-09T14:25:44.003

1

That's the difference between

an undefined value, or a variable whose value is undefined (that's what can check angular.isDefined)
an undefined variable : any reference to its name is a reference error

To check a variable is not defined, do

if (typeof myvariable === "undefined") {

edited Jan 09 '15 at 14:25

answered Jan 09 '15 at 14:20

Denys Séguret

Thanks, but how can I check if the variable is undefined? (your second scenario) – Ben Diamant Jan 09 '15 at 14:22
With a `try`...`catch`? – Dark Falcon Jan 09 '15 at 14:24

score 0 · Answer 2 · answered Jan 09 '15 at 14:30

0

var foo = 'foo';
angular.isDefined(foo) // true;
angular.isDefined(bar) // false
var bar = 'bar';

answered Jan 09 '15 at 14:30

Code Whisperer

2 Answers2