I've made a grave mistake
In a video I published a few weeks ago, I made a rather basic mistake.
Given the following variables...
let threeString = "3";
let threeNum = 3;
What does this expression evaluate to?
threeString + threeNum
If you're smarter than I was an hour ago, you'll know that it evaluates to "33".
Why does it do that?
According to ECMAScript, as summarized by Valentino:
If x is String or y is String then return ToString(x) followed by ToString(y)
In other words, if there is an expression with the + operator, and one of the values is a string, it will always coerce the values into a string.
Final Thoughts
I like to think I'm not completely dumb. I've been building websites/web apps in Javascript for about four years now. However, we all make mistakes. Even the most basic ones! Own up to them, and we'll all learn something. I know I did!
If you want to see my mistake in action, check out the video below!
And the follow up video, which I made before this mistake I made was pointed out...
Top comments (10)
I like to think that intelligent people are really the people able to learn from their mistakes. Good catch on this one. Sharing our mistake is a way of teaching others. Especially for these kind of quirks in JavaScript!
Thank you! I agree.
Type coercion is definitely one of the most confusing parts in JS. It may contain many implicit steps with wtf results. For example
And step by step explanation
My favorite type coercion example
Eugene Karataev ・ Jun 1 ・ 2 min read
I should have included
===in my video. Oops lol. Thank you!More quirks! destroyallsoftware.com/talks/wat
That was hilarious! Thank you for sharing. I wasnt sure what it was before clicking though lol
It gets worse!
Mother of god lol why??
Using "+" before a String converts it to Number in JavaScript
Ridiculous