ES6 doesn't need opt-in

Axel Rauschmayer axel at rauschma.de
Sun Jan 1 09:25:23 PST 2012


> I was challenging Axel's characterization of how JS devs use typeof, since it leads him to conclude that we need to add a bunch of new language features. In code I see, devs don't use typeof for checking a value is null or undefined, so don't base new language features on this use case.

My intention was to list all use cases, to see where typeof could possibly be useful (i.e., to assert its merits). Should it be better to replace it with something else, then there might not be a need to fix typeof null.

> I agree that the common practice of testing if(!name) has pitfalls. But doesn't the common practice suggest that more elaborate features will not help? We need something as simple as if (!name).

Default parameter values should mostly take care of this. The default operator also looks useful (if extended to include null):
http://wiki.ecmascript.org/doku.php?id=strawman:default_operator

It might make sense to add ?? as a unary operator:
    var myvar;
    console.log(?? myvar); // false
    console.log(?? globalUnknown); // false
    var obj = {};
    console.log(?? obj.prop); // false

If something non-grawlixy is preferred, one could give it a name such as `exists`. Furthermore, it might be more consistent with
     value ?? default
to make ?? a postfix operator, but I can’t judge the grammatical implications of that.

-- 
Dr. Axel Rauschmayer
axel at rauschma.de

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