[javascript] How to write an inline IF statement in JavaScript?

How can I use an inline if statement in JavaScript? Is there an inline else statement too?

Something like this:

var a = 2;
var b = 3;

if(a < b) {
    // do something
}

In plain English, the syntax explained:

if(condition){
    do_something_if_condition_is_met;
}
else{
    do_something_else_if_condition_is_not_met;
}

Can be written as:

condition ? do_something_if_condition_is_met : do_something_else_if_condition_is_not_met;

Isn't the question essentially: can I write the following?

if (foo)
  console.log(bar)
else
  console.log(foo + bar)

the answer is, yes, the above will translate.

however, be wary of doing the following

if (foo)
  if (bar)
    console.log(foo)
  else 
    console.log(bar)
else 
  console.log(foobar)

be sure to wrap ambiguous code in braces as the above will throw an exception (and similar permutations will produce undesired behaviour.)

You can also approximate an if/else using only Logical Operators.

(a && b) || c

The above is roughly the same as saying:

a ? b : c

And of course, roughly the same as:

if ( a ) { b } else { c }

I say roughly because there is one difference with this approach, in that you have to know that the value of b will evaluate as true, otherwise you will always get c. Bascially you have to realise that the part that would appear if () { here } is now part of the condition that you place if ( here ) { }.

The above is possible due to JavaScripts behaviour of passing / returning one of the original values that formed the logical expression, which one depends on the type of operator. Certain other languages, like PHP, carry on the actual result of the operation i.e. true or false, meaning the result is always true or false; e.g:

14 && 0          /// results as 0,  not false
14 || 0          /// results as 14, not true
1 && 2 && 3 && 4 /// results as 4,  not true
true && ''       /// results as ''
{} || '0'        /// results as {}

One main benefit, compared with a normal if statement, is that the first two methods can operate on the righthand-side of an argument i.e. as part of an assignment.

d = (a && b) || c;
d = a ? b : c;

if `a == true` then `d = b` else `d = c`

The only way to achieve this with a standard if statement would be to duplicate the assigment:

if ( a ) { d = b } else { d = c }

You may ask why use just Logical Operators instead of the Ternary Operator, for simple cases you probably wouldn't, unless you wanted to make sure a and b were both true. You can also achieve more streamlined complex conditions with the Logical operators, which can get quite messy using nested ternary operations... then again if you want your code to be easily readable, neither are really that intuative.

You could do like this in JavaScript:

a < b ? passed() : failed();

FYI, you can compose conditional operators

var a = (truthy) ? 1 : (falsy) ? 2 : 3;

If your logic is sufficiently complex, then you might consider using an IIFE

var a = (function () {
  if (truthy) return 1;
  else if (falsy) return 2;
  return 3;
})();

Of course, if you plan to use this logic more than once, then you aught to encapsulate it in a function to keep things nice and DRY.

<div id="ABLAHALAHOO">8008</div>
<div id="WABOOLAWADO">1110</div>

parseInt( $( '#ABLAHALAHOO' ).text()) > parseInt( $( '#WABOOLAWADO ).text()) ? alert( 'Eat potato' ) : alert( 'You starve' );

inline if:

(('hypothesis') ? 'truthy conclusion' : 'falsey conclusion')

truthy conclusion: statements executed when hypothesis is true

falsey conclusion: statements executed when hypothesis is false

your example:

var c = ((a < b) ? 'a<b statements' : '!(a<b) statements');

To add to this you can also use inline if condition with && and || operators. Like this

var a = 2;
var b = 0;

var c = (a > b || b == 0)? "do something" : "do something else";

For writing if statement inline, the code inside of it should only be one statement:

if ( a < b ) // code to be executed without curly braces;

I often need to run more code per condition, by using: ( , , ) multiple code elements can execute:

var a = 2;
var b = 3;
var c = 0;

( a < b ?  ( alert('hi'), a=3, b=2, c=a*b ) : ( alert('by'), a=4, b=10, c=a/b ) );

If you just want an inline IF (without the ELSE), you can use the logical AND operator:

(a < b) && /*your code*/;

If you need an ELSE also, use the ternary operation that the other people suggested.

There is a ternary operator, like this:

var c = (a < b) ? "a is less than b"  : "a is not less than b";