Why does Node.js' Assert.js use !!!value in their code? What purpose does it serve? [duplicate]

Question

function ok(value, message) {
  if (!!!value) fail(value, true, message, '==', assert.ok);
}
assert.ok = ok;

!!!value basically means not not not Boolean(value) yes?

Say if value = 9 > 1, then it would mean: not not not true.

not true = false
not not true = true
not not not true = false

My brain hurts. Why don't they just use !value instead of !!!value?

Answer 1

!value and !!!value both do have the same effect.

But, they intenionally use !! to convert the potential 'truthy' or 'falsy' variable value to a boolean.

So it does makes sense to use !!! when using value as a negated boolean, so developers can see that (in this case) value may only be 'truthy', e.g. a string and not true.

If in refactoring someone needs to set something to true and uses value, it may be set to a string. The !!! tells him to use !!value, if he expects value as a boolean.

Answer 2

The likely answer is either that they're using it to draw emphasis to the conversion or that some programmer just thought it was funny at some point -- there's absolutely no syntactical difference between !x and !!!x (or !!!!!!!!!!!!!x for that matter). After the first ! which will convert the variable to a boolean, you're just repeatedly adding the not operator to something. All that matters is whether it's negated an even or odd number of times.