Tutorial: If and Else Statements in JS

**kirupa** · December 14th, 2011, 02:22 AM

Hi everyone,
This is the happening place to discuss all things related to the If and Else Statements in JS tutorial.

Cheers,
Kirupa

**kadaj** · December 14th, 2011, 05:08 AM

Please add some notes on triple equal '==='.

Originally Posted by Crockford

=== and !== Operators.

It is almost always better to use the === and !== operators. The == and != operators do type coercion. In particular, do not use == to compare against falsy values.

I want triple equals

.

Does ternary operator includes here? Or that can be another tutorial on conditionals.

**Krilnon** · December 14th, 2011, 05:20 AM

Here's another case where I disagree with Crockford. I know exactly how == and === differ, have known for years, and still find that == is almost always what I want and intend. However, I wouldn't try to convince people to use one over the other like he has (in my opinion, unfortunately) done.

**kadaj** · December 14th, 2011, 10:44 PM

So you are saying that there is no point in all the javascript conventions written by Crockford? And Ecma-262 5.1 Edition is the holy grail of JavaScript and there is no point in JavaScript The Good Parts by Crockford?

**Krilnon** · December 15th, 2011, 03:16 AM

Nope, I'm just disagreeing with this one piece of his advice. (I said 'another' because there was another of his pieces of advice mentioned recently in a different thread.) I'm not saying anything as sensational as you're implying.

**Swooter** · December 15th, 2011, 03:09 PM

Maybe it's good to point out that there are ways to write 'if' and 'if/else' statements using shorter syntax.
Not that I recommend to use them, as they are hard to read, but it's a good thing to know what these statements do...
A few examples:

Short IF

Code:

if (variable_1 == 80) alert("something");

Short IF

Code:

(variable_1 == 80) && alert("something");

Short OR

Code:

variable_1 = some_property || 0;

Short if/else

Code:

alert( (variable_1==80) ? 'eighty' : 'not eighty' );

Short if/else

Code:

variable_1 = some_property ? 1 : 0;

**TheCanadian** · December 15th, 2011, 06:37 PM

Originally Posted by Krilnon

Nope, I'm just disagreeing with this one piece of his advice. (I said 'another' because there was another of his pieces of advice mentioned recently in a different thread.) I'm not saying anything as sensational as you're implying.

But using the strict equality operator is best practice

**kirupa** · December 15th, 2011, 09:53 PM

Originally Posted by Swooter

Maybe it's good to point out that there are ways to write 'if' and 'if/else' statements using shorter syntax.
Not that I recommend to use them, as they are hard to read, but it's a good thing to know what these statements do...
A few examples:

Short IF

Code:

if (variable_1 == 80) alert("something");

Short IF

Code:

(variable_1 == 80) && alert("something");

Short OR

Code:

variable_1 = some_property || 0;

Short if/else

Code:

alert( (variable_1==80) ? 'eighty' : 'not eighty' );

Short if/else

Code:

variable_1 = some_property ? 1 : 0;

That is a great suggestion! I've added a note to the end of the tutorial with a pointer to your post

**TheCanadian** · December 16th, 2011, 06:35 AM

I think it would make sense to say in this tutorial that the condition for an if statement doesn't necessarily need to be a comparison between two operands. It can be any expression that evaluates to a boolean. It would then probably make sense to say what different literal values and complex objects resolve to when coerced.

Originally Posted by Krilnon

Nope, I'm just disagreeing with this one piece of his advice. (I said 'another' because there was another of his pieces of advice mentioned recently in a different thread.) I'm not saying anything as sensational as you're implying.

I just read some stuff by him and I disagree with a lot of it, mostly because I think a lot of it has no reason and is just an attempt to create an arbitrary convention. Not that following a standard is bad per se, he just makes it seem like what he's saying is absolute truth. But I may be misinterpreting the tone of the article.

**Krilnon** · December 16th, 2011, 07:11 AM

Originally Posted by TheCanadian

It can be any expression that evaluates to a boolean.

It can be any expression. And any expression can be evaluated and converted to be a boolean value. (This might have been exactly what you were saying in your post, but the way that I read your post seemed to imply that there are some expressions that you couldn't use in an if statement.)

I agree that the additional explanation that you suggested for the tutorial would be useful.

Originally Posted by TheCanadian

he just makes it seem like what he's saying is absolute truth. But I may be misinterpreting the tone of the article.

I interpret his tone in the same way!