I’ve always had to put
null in the else conditions that don’t have anything. Is there a way around it?
condition ? x = true : null;
Basically, is there a way to do the following?
condition ? x = true;
Now it shows up as a syntax error.
FYI, here is some real example code:
!defaults.slideshowWidth ? defaults.slideshowWidth = obj.find('img').width()+'px' : null;
First of all, a ternary expression is not a replacement for an if/else construct – it’s an equivalent to an if/else construct that returns a value. That is, an if/else clause is code, a ternary expression is an expression, meaning that it returns a value.
This means several things:
- use ternary expressions only when you have a variable on the left side of the
=that is to be assigned the return value
- only use ternary expressions when the returned value is to be one of two values (or use nested expressions if that is fitting)
- each part of the expression (after ? and after : ) should return a value without side effects (the expression
x = truereturns true as all expressions return the last value, but it also changes x without x having any effect on the returned value)
In short – the ‘correct’ use of a ternary expression is
var resultofexpression = conditionasboolean ? truepart: falsepart;
Instead of your example
condition ? x=true : null ;, where you use a ternary expression to set the value of
x, you can use this:
condition && (x = true);
This is still an expression and might therefore not pass validation, so an even better approach would be
void(condition && x = true);
The last one will pass validation.
But then again, if the expected value is a boolean, just use the result of the condition expression itself
var x = (condition); // var x = (foo == "bar");
In relation to your sample, this is probably more appropriate:
defaults.slideshowWidth = defaults.slideshowWidth || obj.find('img').width()+'px';