Template literal propery names in object literals

# Alex Kodat (13 days ago)

Just curious. Is there a reason template literals are not allowed as property names in object literals? I can do:

let obj = {'foo bar': 1};

and

let obj = {"foo bar": 1};

but not

let obj = {foo bar: 1};

It doesn't seem that allowing the latter would present any syntactic problems and seems like almost an oversight that it's not allowed.

The main reason I ask is that we've gone completely over to using template literals for all our literals (why not?) and was surprised that we can't use a template literal as an object literal property name. Obviously, we can do:

let obj = {[foo bar]: 1};

And given that square brackets allow arbitrary expressions for propery names, it wouldn't seem that supporting template literals for object literal property names would not present any daunting implementation issues.

I guess I'd argue that the Principle of Least Astonishment and/or completeness suggests that JS should support this.

Sorry if this has been asked before but couldn't find anything in the archive.

Thanks


Alex Kodat Senior Product Architect Rocket Software t: +1 781 684 2294 • m: +1 315 527 4764 • w: www.rocketsoftware.com

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# Gus Caplan (13 days ago)

Related discussion tc39/ecma262#1399

# Alex Kodat (13 days ago)

Thanks Gus,

Good stuff. Though I think I’d take a different tack on the discussion at that link, especially as I think the template literals should allow substitutions (why not?):

let obj = { ${Date()}: 1};

I guess the tack I would take in the spec would be to add TemplateLiteral to ComputedPropertyName and not worry about whether or not it's a NoSubstitutionTemplate.

Thanks


Alex Kodat Senior Product Architect Rocket Software t: +1 781 684 2294 • m: +1 315 527 4764 • w: www.rocketsoftware.com

From: Gus Caplan <me at gus.host>

Sent: Thursday, November 7, 2019 11:13 AM To: Alex Kodat <akodat at rocketsoftware.com>

Cc: es-discuss at mozilla.org Subject: Re: Template literal propery names in object literals

Related discussion nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftc39%2Fecma262%2Fissues%2F1399&data=02|01||9e20b9f578574ad67b1308d763a5b814|79544c1eed224879a082b67a9a672aae|0|1|637087435736614052&sdata=xDiwNTWHvdfIakrVFe6RmiP5pLHzC0i%2BoRNwKgvTMvc%3D&reserved=0

On Thu, Nov 7, 2019 at 8:46 AM Alex Kodat <mailto:akodat at rocketsoftware.com> wrote:

Just curious. Is there a reason template literals are not allowed as property names in object literals? I can do:

let obj = {'foo bar': 1};

and

let obj = {"foo bar": 1};

but not

let obj = {foo bar: 1};

It doesn't seem that allowing the latter would present any syntactic problems and seems like almost an oversight that it's not allowed.

The main reason I ask is that we've gone completely over to using template literals for all our literals (why not?) and was surprised that we can't use a template literal as an object literal property name. Obviously, we can do:

let obj = {[foo bar]: 1};

And given that square brackets allow arbitrary expressions for propery names, it wouldn't seem that supporting template literals for object literal property names would not present any daunting implementation issues.

I guess I'd argue that the Principle of Least Astonishment and/or completeness suggests that JS should support this.

Sorry if this has been asked before but couldn't find anything in the archive.

Thanks


Alex Kodat Senior Product Architect Rocket Software t: +1 781 684 2294 • m: +1 315 527 4764 • w: nam01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.rocketsoftware.com&data=02|01||9e20b9f578574ad67b1308d763a5b814|79544c1eed224879a082b67a9a672aae|0|1|637087435736623994&sdata=hTNIou6kPg5Ms%2FnIK%2BFVjrWa7mcGDtAbSJrVLVufxQU%3D&reserved=0

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# Jordan Harband (13 days ago)

Anything dynamic - computed - should be in brackets, since that's what that indicates.

Thus, template literals with substitutions must require brackets.

Based on sentiments like tc39/ecma262#1399, either all template literals or none should be permitted in a given position.

Thus, no change is possible.