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  • Setting up (non-index) properties of arrays

Setting up (non-index) properties of arrays

# Axel Rauschmayer (13 years ago)

As an example, a template string call site ID would be constructed as follows:

const callSiteId1234 = do {
    let literalParts = ['lit1\n', ' lit2 ', ''];
    literalParts.raw = ['lit1\\n', ' lit2 ', ''];
    literalParts
};

How about the following abbreviation?

const callSiteId1234 = ['lit1\n', ' lit2 ', '', raw: ['lit1\\n', ' lit2 ', '']];

Not sure it’s a frequent-enough use case, though. Mustache would be nice here, or one could use Underscore:

const callSiteId1234 = _.extend(['lit1\n', ' lit2 ', ''], {raw: ['lit1\\n', ' lit2 ', '']});
# Brendan Eich (13 years ago)

The desugaring in the wiki proposal must not be observable.

Separately, we've long entertained extending array literals to encompas ad-hoc properties (expandos). Also the dict strawman wants [a:1,b:2] syntax. I think expandos on arrays are rare enough that dicts should win, if it comes down to a future-proofing fight.

# Brendan Eich (13 years ago)

Brendan Eich wrote:

The desugaring in the wiki proposal must not be observable.

Indeed I don't believe Allen is spec'ing template strings via desugaring at all.

# Axel Rauschmayer (13 years ago)

Separately, we've long entertained extending array literals to encompas ad-hoc properties (expandos). Also the dict strawman wants [a:1,b:2] syntax. I think expandos on arrays are rare enough that dicts should win, if it comes down to a future-proofing fight.

Agreed on rareness. If dicts are only maps from string to value [1] (a safe object-as-map, if you will) then I don’t think we need a literal/initializer syntax for that – they can easily be initialized via object literals, e.g.: dict({ a: 1, b: 2 })

However, [a:1,b:2] or {| a: 1, b: 2 |} would be great as a literal syntax for maps (from value to value). That is, a and b would be identifiers and not string keys. But that must make parsing difficult. Even something very restrictive (such as: parens if there is more than one token in the expression) does not seem much help.

[1] strawman:dicts

# Allen Wirfs-Brock (13 years ago)

On Aug 4, 2012, at 12:06 AM, Axel Rauschmayer wrote:

... How about the following abbreviation?

const callSiteId1234 = ['lit1\n', ' lit2 ', '', raw: ['lit1\\n', ' lit2 ', '']];

Or, using :=

const callSiteId1234 = ['lit1\n', ' lit2 '] := {raw: ['lit1\n', ' lit2 ', ''};

(ignoring all the other issues about why this isn't a great example)