Use with?

[wesleytodd]

Typically I wouldn't ever recommend using with, but in this case it seems like it would improve the api of this module to switch to something like this:

module.exports = (templateStr) => return new Function('d', 'with (d) { return `' + templateStr + '` }');

The performance hit is pretty minimal (see below), and it does not force users to have that d. strewn through their templates. What do you think? Or is the performance aspect the main focus of this package?

Here is the perf test I did:

$ cat template-literal.js
var tmplWith = (str) => new Function('d', 'with (d) { return `' + str + '` }');
var tmplWithout = (str) => return new Function('d', 'return `' + str + '`');

var time = (fnc) => {
  console.time(fnc.name);
  for (let i = 0; i < 10000; i++) fnc.call(null, i);
  console.timeEnd(fnc.name);
};
time(function runWith (i) {
	tmplWith('i: ${i}')({ i });
});
time(function runWithout (i) {
	tmplWithout('i: ${d.i}')({ i });
});

$ node template-literal.js
node template-literal.js
runWith: 16.748ms
runWithout: 11.198ms

[Drulac]

That have a little performance impact on compilation, but the impact is huge on running :

With : Literal render x 455,629 ops/sec ±0.20% (84 runs sampled)
Without : Literal render x 3,278,679 ops/sec ±0.44% (81 runs sampled) 

It became 7 times more long... It's a good improvement, I think the performance loss is to high to add it.

(In the bench/ directory there is compile.js who is perfect to benchmark, you can comment other frameworks' tests to win time)

[wesleytodd]

Ok, so performance is your biggest concern for this module then. That is why I asked, because it is obviously slower to use with. My very minimal test did not show such poor performance as yours did or I wouldn't have even brought it up. The performance hit probably scales with the number of variable lookup's.

Anyway, I just thought it was worth bringing up because the hard coded d variable for access inside the templates seemed less user friendly than the with version.

[Drulac]

You have only tested template compilation, who run one time in an application, I have run template rendering, who run at each page load ;-) Yes I know it may be not friendly at first use, but the performance decrease is too high to add it :-/

[Drulac]

But I can add an option to choose the name of the variable, with `d` as default value ?

[wesleytodd]

I tested compilation and rendering in one go. I agree that is not technically accurate to a use case, it was just my 2 second look at what the perf difference would be. I probably wont be using the module anyway, just thought I would give my feedback since you posted over on the express repo. But I do think that adding the option to change the variable name might help with other people wanting to use this, again just my 2c.

[Drulac]

Thanks for you feedback :-)

I'm french, and not really good at english, I havn't understand "again just my 2c" 😅

[wesleytodd]

Haha, no worries. "just my 2c" is an English saying which means "I am giving my personal opinion". See https://en.wikipedia.org/wiki/My_two_cents

[Drulac]

Oh ok thanks for explainations :-)