Quasi-literals for templating?

Brendan Eich brendan at mozilla.com
Wed Jun 15 09:05:36 PDT 2011

On Jun 15, 2011, at 8:36 AM, Axel Rauschmayer wrote:

>> The point is that the callSiteId captures all the literal/constant/loop-invariant parts of the quasi, both raw and cooked ("expandedLP"). The remaining quasi handler parameters are the necessarily variable, evaluated-at-runtime substitution expression results.
> That makes sense. The ID then allows one to do caching. But I don’t see how the same quasi-literal can be “invoked” multiple times.

In a loop:

  for (let i = 0; i < N; i++) {
    let sub0 = i * 2, sub1 = i * i;

    results[i] = re_match`lp0${sub0}lp1${sub1}lp2`(targets[i]);

Remember the quasi handler is just a function, here named re_match, found as usual by lexical scope. The invariant parts (raw and cooked) are collected and hoisted, given a unique name behind the scenes so they can be passed as an object, as the first actual parameter. The remaining arguments are sub0 and sub1evaluation results, which definitely vary per iteration.


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