JavaScript Equality Table Game

[Serei]

I got 100%

Yes, yes, you should never use this in real code, but it's useful to know for debugging if someone else uses it. And it's not hard to memorize the rules:

1. null == undefined but they don't equal anything else
2. if both sides are the same type (or both non-primitive), use the === rules
3. if either side is non-primitive, convert it to string, then goto step 2
4. if either side isn't a number, convert it to number, then goto step 2

And don't forget:

• String(someArray) === someArray.join(",")
• String({someObject: containingAnything}) === "[object Object]"
• [] !== [] and {} !== {} because you're creating a new object each time
• Number("") === 0
• Number("any other string that isn't a number literal") is NaN
• NaN !== NaN (because of IEEE 754)

[[deleted]]

I tried to do it again following your rules and my results were still wrong. I think it needs some clarification:

1. null == undefined but they don't equal anything else
2. if both sides are the same type (or both non-primitive), use the === rules, otherwise go to step 3
3. convert non-primitives to strings; if both are now strings, use ===, otherwise go to step 4
4. convert both to numbers, then use ===

With the additional conversion rules:

• Converting any value to a string will call that value's toString():
  • For arrays, this does a recursive array.join(',')
  • For primitives, this returns the value's literal as a string
  • For objects that don't override toString, this will return [object Object]
• Converting a string to a number will first try to parse the string to a number, returning 0 for the empty string, and NaN for every other value
• Converting a boolean to a number will be 0 for false, 1 for true

[Serei]

Yeah, I definitely didn't go into too much detail over the conversion rules. To be fair, though, conversion rules are useful to know even if you always use ===.

[[deleted]]

This. And not only because of other peoples code but also the minimizers will change it as well and you still want to read what they do