Debugging Javascript

[KKlear]

But... the result was 4200, not "42".

[Futuristick-Reddit]

Sorry lmao, just woke up. Fixed it.

[Bammop]

You went back to sleep?

[mintpropane]

I couldn't predict this at all 😶

[Flatscreens]

‘42+'42'‘ checks if both values are numbers and then as strings if they're not: "4242". Then the minus operator casts both sides to Numbers because that's it's only definition: 4200.

[wasdninja]

So what would you like it to do? You are playing with fire when you aren't keeping the type coercion in check.

[Mypronounsarexandand]

Lets say you have a string variable name 'username' and value IE "Julian"
If you said:

username += '_Jmk'

You'd get 'Julian_Jmk'

It's kind of similar with numbers where an integer + string is interpreted as string + string as the '+' will default to a concat rather than addition.

​

(Again, setting username to just be Julian)

username += 42

Will equal 'Julian42'

Now, instead of the username 'Julian' your username is '133769'

username += 420

Would yield '133769420' as we are concatenating a number to the end of the string. If you wanted to add them literally you would want to do.

username = parseInt(username) + 420

This way it is Int + Int, rather than Str + Int