True — though I’m not sure why concern for this case would merit new syntax. Have you found that to be a common source of problems? Usually setters are light / idempotent.
(Not opposed to the premise btw — just trying to hear more about what problems it would solve, especially since syntactic solutions usually have to be pretty high-value or else address something which can’t be solved any other way.) On Wed, Jul 4, 2018 at 8:41 PM Jacob Pratt <[email protected]> wrote: > Sure, you'd be making an assignment no matter what in that case, which > would unnecessarily trigger the setter, possibly causing side effects. > > ``` > const obj = { > get x() { > return _x; > }, > > set x(value) { > console.log('setter called'); > _x = value; > }, > > demo(params = {}) { > ({ x: this.x = this.x } = params); > }, > }; > > obj.demo({ x: 5 }); > obj.demo({ x: undefined }); > ``` > > This will log twice, where it only needs to trigger it once. > > jhpratt > > On Wed, Jul 4, 2018 at 8:16 PM, Darien Valentine <[email protected]> > wrote: > >> > My thought was to have the following: this.foo ?= params?.foo; which >> can be desugared to if (($ref = params?.foo) !== undefined) { this.foo = >> $ref; } >> >> Are there any specific advantages to the new syntax you’re describing? >> Initially, it appears to me like a less powerful form of an existing >> syntactic feature — default initializers and binding patterns allow >> expressing the same logic: >> >> ``` >> const obj = { >> demo(params={}) { >> ({ foo: this.foo=this.foo } = params); >> >> console.log( >> `params was ${ JSON.stringify(params) }; ` + >> `this.foo is now ${ JSON.stringify(this.foo) }` >> ); >> } >> } >> >> obj.demo({ foo: 1 }); >> obj.demo({}) >> obj.demo({ foo: 2 }); >> obj.demo(); >> obj.demo({ foo: 3 }); >> obj.demo({}); >> ``` >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> >> >
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