javascript question mark ?: logical syntax, defensive programming

Question

I am trying to re-write the statement below using the javascript ?: syntax.

if(type of someVariable !="undefined"){
     someFunction(someVariable);
}else{}

This is my current attempt and it's causing a syntax error

typeof someVariable != "undefined" ? someFunction(someVariable) : ;

If any one can tell met what I'm doing wrong I'd appreciate it. Any accompanying tips on best practices for defensive programing are welcome.

broofa · Answer 1 · 2013-11-07T18:49:27.393

5

?: style (requires expressions on either side of the :):

typeof(someVariable) != 'undefined' ? someFunction : null;

Ninja-style:

someVariable !== undefined && someFunction(someVariable);

[Edit: I couldn've sworn noop was a thing in Javascript, but apparently I was wrong. Switched to null]

edited Nov 07 '13 at 18:49

answered Nov 07 '13 at 02:23

broofa

Khamidulla · Answer 2 · 2013-11-07T02:39:36.203

0

It should look like this.

someVariable != undefined ? someFunction(someVariable):someOtherfunction(someOtherVarialbe);

if you do not want else statement and want it in single line you can do like this:

  if(someVariable != undefined){someFunction(someVariable);}

edited Nov 07 '13 at 02:39

answered Nov 07 '13 at 02:26

Khamidulla

1

`typeof` isn't a function. You don't need the `()` after it. And it returns a string, so you need to compare to `"undefined"`. But better to just do `someVariable != undefined`. – Blue Skies Nov 07 '13 at 02:31

score 0 · Answer 3 · edited May 23 '17 at 10:24

0

even though the ternary operation controls the program flow, I'd use it only in assignment operation or when returning a value from a function.

edited May 23 '17 at 10:24

Community

answered Nov 07 '13 at 02:31

Guy Gavriely

3 Answers3