Can the value of JavaScript's "if" statement be used?

Question

If you enter the following into Firefox's Browser Console, the result is 456:

if (false) { 123; } else if (true) { 456; } else { 789; }

If you adjust the true/false combinations, you can also get 123 or 789 as a result. However, if you try and do something like:

var a = if (false) { 123; } else if (true) { 456; } else { 789; };

you just get a syntax error. The syntax error doesn't surprise me, but I'm wondering what the point is of if statements having a value if that value can't be used.

So my question is: can an if statement be used as an expression, and if so, how?

EDIT: Thanks for the responses so far, but just to be absolutely clear, I know I could use functions and/or the ternary operator to achieve what I've described, but I specifically want to know whether the 'return value' of an if statement can be used, i.e. whether an if statement can be used as an expression. I'm not asking for alternative ways of setting a value based upon various conditions.

(And if an if cannot be used as an expression, then why does Firefox's Browser Console show a value for the first example above?)

the else part is unreachable in your second case – Voonic Oct 22 '13 at 11:15 — Voonic, Oct 22 '13 at 11:15
Yeah, I realise that thanks - these are just examples! – IpsRich Oct 22 '13 at 11:37 — IpsRich, Oct 22 '13 at 11:37

score 3 · Answer 1 · answered Oct 22 '13 at 10:53

3

You can use ternary operators:

var a = false ? 123 : true ? 456 : 789;

answered Oct 22 '13 at 10:53

David Hedlund

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Thanks, I would usually use the ternary operator, but my question is specifically about the `if` statement. – IpsRich Oct 22 '13 at 11:38

Savv · Answer 2 · 2013-10-22T10:55:32.193

0

have as a function instead:

function a(b) //where b is your boolean
{
   if(b)
   {
      return 123;
   }
   else
   {
      return 456;
   }
}

edited Oct 22 '13 at 10:55

answered Oct 22 '13 at 10:55

Savv

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7

score 0 · Answer 3 · edited May 23 '17 at 12:28

0

Use a ternary operator: var x = (true ? 432 : 765); // will set x to 432

See also JavaScript ternary operator example with functions

edited May 23 '17 at 12:28

Community

1
1

answered Oct 22 '13 at 10:55

steenbergh

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score 0 · Answer 4 · answered Oct 22 '13 at 11:09

0

Use function instead of directly using that expression. And then you also have to return those values.

 
var a=function(){if (false) { return 123; } else if (true) { return 456; } else { return 789; }}
alert(a());

answered Oct 22 '13 at 11:09

swapnil

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3

Can the value of JavaScript's "if" statement be used?

4 Answers4