How to call native es6 template string replacement

问题:

I'm writing a es6 tag function for template literals, which first checks a condition in the string and, if the condition isn't found, merely interprets the template literal as if it were untagged. I am curious if, from my tag function, there is a way to call the browser's native template literal function (which I assume would be faster than my own implemented function). Bonue: With this, couldn't there be an opportunity for tag composition, eg htmlEscape(unindentfoobar);

eg.

function dumbTag(strs, ...vals) {
    vals = vals.map((val,i) =>
            (i % 2 == 0 ? 'even:' : 'odd:')+val);
    return String.template(strs, ...vals);
}

my own implemented function - is there a faster way / way to call what the browser does?

function template(strs, ...vals) {
    let result = strs[0];
    for (let [i,val] of vals.entries()) {
        result += val;
        result += strs[i+1];
    }
    return result;
}

回答1:

There is no such builtin function - untagged template literals are just evaluated straight to strings.

is there a faster way?

That depends a lot on the implementation. In case you are using a transpiler, I would avoid using rest parameters, iterators and for of loops:

function template(strs) {
    var result = strs[0];
    for (var i=1; i < strs.length; i++) {
        result += arguments[i];
        result += strs[i];
    }
    return result;
}

回答2:

You can (ab)use String.raw (the only built-in tag) for this purpose:

function doNothingTag() {
  arguments[0] = { raw: arguments[0] };
  return String.raw(...arguments);
}

doNothingTag`It works!`
// "It works!"

doNothingTag`Even\nwith\nescape\nsequences!`
// "Even
// with
// escape
// sequences!"

This is essentially just tricking String.raw into thinking that the escape-interpreted string is the raw version.