What is the meaning of “<-” in JS

Question

in the following code snippet I'd expect an error, but false is returned. Why?

foo = {}
foo <- "lel"

returns false

It certainly is not comparing which one is larger, so what is it doing?

Answer 1

<- doesn't mean anything as a single token. You have < (less than) followed by - (unary - = negation) applied to "lel" . Eg:

foo < -"lel"

It's false because -"lel" is NaN *, and all comparisons with NaN are false (even equality, eg NaN === NaN is false).

(It happens that foo gets coerced to number by the < as well [that's what < and > do when one of the operands is of type number and the other isn't]. And that coercing {} to number also yields NaN . So the final step is NaN < NaN which is false because, again, all comparisons with NaN are false.)

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* ...because applying a unary - or + to a string coerces that string to number; "lel" coerces to NaN , and then negating that gives you NaN because like comparisons, all math ops on NaN result in NaN .