5 ms·

This one really gets to me. f = 0 (type: object, constructor: Number) 0<!f = false 0<!-f = true

• eyelidlessness 5y ago
  I’ve tried three times to write why I think this is, and each time I get lost in my reasoning. Alas, I’ve been on mobile for this whole thread and I don’t have any more brain cells to try to code like this tonight lol
  • Leszek 5y ago
    It's because `f = new Number(0)` is a boxed number (therefore it's an object), and `!f` calls ToBoolean on this object which unconditionally returns true (https://tc39.es/ecma262/#table-toboolean-conversions https://tc39.es/ecma262/#table-toboolean-conversions). `!-f` first applies unary minus, which first performs a ToNumber on the f object (which returns unboxed 0), that's negated to -0, and then ToBoolean of -0 is false.
    • LordDragonfang 5y ago
      See also: https://dorey.github.io/JavaScript-Equality-Table/ https://dorey.github.io/JavaScript-Equality-Table/ I particularly like the note on the "if" tab: > Note: This row does not match up with any of the rows in the other table.