Yeah I guess there exists a use case for that method still. But I don’t feel that use case merits special syntax.
> On 12 Jan 2019, at 16:25, Isiah Meadows <[email protected]> wrote: > > I'd just prefer a way to detect the value `undefined` vs no such binding. >> On Sat, Jan 12, 2019 at 10:26 Sultan <[email protected]> wrote: >> >const [variable = defaultValue] = [maybeUndefinedValue] >> >> This would fail throw for variables you don't know exist i.e in the >> following example polyfill will throw if Symbol doesn't exist. >> >> const [Symbol = SymbolPolyfill] = [Symbol] >> >> This is specifically why convention is to use: >> >> typeof maybeUndefinedValue === 'undefined' >> >> >const fn = ({ key = defaultValue }) => { console.log(key); } >> >> The second example doesn't assign the key prop to the passed object. >> >> >>> On Sat, Jan 12, 2019 at 5:54 PM Rob Ede <[email protected]> wrote: >>> pretty succinct with existing de-structuring syntax: >>> >>> ``` >>> const [variable = defaultValue] = [maybeUndefinedValue] >>> >>> const fn = ({ key = defaultValue }) => { console.log(key); } >>> ``` >>> >>>> On 11 Jan 2019, at 12:00, [email protected] wrote: >>>> >>>> Send es-discuss mailing list submissions to >>>> [email protected] >>>> >>>> To subscribe or unsubscribe via the World Wide Web, visit >>>> https://mail.mozilla.org/listinfo/es-discuss >>>> or, via email, send a message with subject or body 'help' to >>>> [email protected] >>>> >>>> You can reach the person managing the list at >>>> [email protected] >>>> >>>> When replying, please edit your Subject line so it is more specific >>>> than "Re: Contents of es-discuss digest..." >>>> Today's Topics: >>>> >>>> 1. Syntax operator for "default assignment if value doesn't >>>> exits" (Sultan) >>>> >>>> From: Sultan <[email protected]> >>>> Subject: Syntax operator for "default assignment if value doesn't exits" >>>> Date: 11 January 2019 at 10:52:12 GMT >>>> To: es-discuss <[email protected]> >> >>>> >>>> >>>> An operator syntax for the the "typeof" pattern used to detect if a >>>> environment/object has a value: >>>> >>>> if (typeof variable === 'undefined') {...} >>>> if (typeof object.key === 'undefined') {...} >>>> >>>> This could manifest in destructuring as the following >>>> >>>> var fn = ({ key ||= 1 }) => { >>>> } >>>> >>>> And with variables as: >>>> >>>> var global ||= {} >>>> >>>> Equivalent code: >>>> >>>> (arg) => { >>>> if (typeof arg.key === 'undefined') { >>>> arg.key = 1 >>>> } >>>> } >>>> >>>> if (typeof global === 'undefined') { >>>> var global = {} >>>> } >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> es-discuss mailing list >>>> [email protected] >>>> https://mail.mozilla.org/listinfo/es-discuss >>> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss
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