It drives me crazy when I see code where someone is checking a boolean to see if it is true or not and they write it like this.

  if(isValid == true)
//Do something.

Noooooo. Stop it! Of course true equals true. Just eliminate the condition part and check the value of the boolean.

//Do something.

If you just want to check for false, then do this

//Do something.

If you know anyone who is doing this wrong, share this post with them.


It has been pointed out to me by many people on LinkedIn and the wider internet that I failed to mention the problems with dynamic languages like JavaScript and PHP, as well as the problems with nullable booleans in stongly typed languages like C#.

Why this doesn't work with PHP and JavaScript?

//Without Equals:
$boolean = true - if ($boolean) {} //true
$string = (string) 'Hello world' - if ($string) {} //true
$integer = (int) 2345 - if ($integer) {} //true
$class = new stdClass() - if ($class) {} //true
$boolean = false - if ($boolean) {} //false
$string = (string) '' - if ($string) {} //false
$integer = (int) 0 - if ($integer) {} //false
$class = null - if ($class) {} //false
//With double equal (==):
$boolean = true - if ($boolean == true) {} //true
$string = (string) 'Hello world' - if ($string == true) {} //true
$integer = (int) 2345 - if ($integer == true) {} //true
$class = new stdClass() - if ($class == true) {} //true
$boolean = false - if ($boolean == true) {} //false
$string = (string) '' - if ($string == true) {} //false
$integer = (int) 0 - if ($integer == true) {} //false
$class = null - if ($class == true) {} //false
//With triple equal (===):
$boolean = true - if ($boolean === true) {} //true
$string = (string) 'Hello world' - if ($string === true) {} //false
$integer = (int) 2345 - if ($integer === true) {} //false
$class = new stdClass() - if ($class === true) {} //false
$boolean = false - if ($boolean === true) {} //false
$string = (string) '' - if ($string === true) {} //false
$integer = (int) 0 - if ($integer === true) {} //false
$class = null - if ($class === true) {} //false
If you want to check that it is really a boolean which is true in PHP you have to do === true so that it checks the type.

Thanks to Mike B for putting this in the comments.




Why this doesn't work for nullable booleans.

A case for using

if(isValid == true)

If you later want to change to a nullable bool. If you declared:

bool? isValid;

and then tried:


you wouldn't be able to compile. If you cast using:


you would get a runtime error. However, if to begin with, you were using:

if(isValid == true)

everything would be fine.

Thanks to Adam for writing this in the comments and on LinkedIn.



From all of the comments around the web that I've managed to read, I have found:

Some people choose to write them like this for style purposes and readability:

if(isValid == true)
//Do something.

Some people like to write them like this to make sure they don't get caught out by using a single equals sign

if(true == isValid)
//Do something.

From now on, if I'm using nullables in C# I will use the null-coalescing operator. Read more about these in my blog post Null-coallescing operator.

if(isValid ?? false)
//Do something.

If I'm writing in JavaScript or PHP I will use the triple equals

if(isValid === true)
//Do something.

If you would like to know more, why not use your 10 day free trial with Pluralsight to go through Clean Code: Writing Code for Humans

Want to thank me?

If I've helped you out and you want to thank me, why not buy me a coffee?

Paul Seal

A .NET Web Developer from Derby (UK) who specialises in building Content Management System (CMS) websites using MVC with Umbraco as a framework. Paul is passionate about web development and programming as a whole. Apart from when he's with his wife and son, if he's not writing code, he's thinking about it or listening to a podcast about it.



Share Top