this proposal is too confusing for users to use correctly. nodejs' util.isNullOrUndefined does the job already.

[kaizhu256]

the more i work with code that has to differentiate between falsey and nullishness, the more i remain convinced its more maintainable to test for nullishness with with an explicit function-call. mixing and matching || and ?? will inevitably lead to spaghetti-code (plus how do you use it in the && case?).

real-world use-case with isNullOrUndefined here:
https://github.com/kaizhu256/node-swgg/blob/2017.10.17/lib.swgg.js#L3647

/*
 * how would ?? help in this use-case?
 */
            if (paramDef.valueEncoded === undefined &&
                    local.isNullOrUndefined(paramDef['x-example'])) {
                paramDef.valueEncoded = local.dbFieldRandomCreate({
                    modeNotRandom: true,
                    propDef: paramDef
                });
            }

[ljharb]

It wouldn't; (without conditional assignment, which isn't part of this proposal) - this use case isn't covered by this proposal nor is it intended to be.

This proposal is particularly useful when looking up values in a chain with maybe-nullish intermediate values; it's not useful for mutating a maybe-nullish value.