Convert a string to a template string

Question

Is it possible to create a template string as a usual string

let a=\"b:${b}\";

an then convert it into a template string

le         


        

Answer 1

Since we're reinventing the wheel on something that would be a lovely feature in javascript.

I use eval(), which is not secure, but javascript is not secure. I readily admit that I'm not excellent with javascript, but I had a need, and I needed an answer so I made one.

I chose to stylize my variables with an @ rather than an $, particularly because I want to use the multiline feature of literals without evaluating til it's ready. So variable syntax is @{OptionalObject.OptionalObjectN.VARIABLE_NAME}

I am no javascript expert, so I'd gladly take advice on improvement but...

var prsLiteral, prsRegex = /\@\{(.*?)(?!\@\{)\}/g
for(i = 0; i < myResultSet.length; i++) {
    prsLiteral = rt.replace(prsRegex,function (match,varname) {
        return eval(varname + "[" + i + "]");
        // you could instead use return eval(varname) if you're not looping.
    })
    console.log(prsLiteral);
}

A very simple implementation follows

myResultSet = {totalrecords: 2,
Name: ["Bob", "Stephanie"],
Age: [37,22]};

rt = `My name is @{myResultSet.Name}, and I am @{myResultSet.Age}.`

var prsLiteral, prsRegex = /\@\{(.*?)(?!\@\{)\}/g
for(i = 0; i < myResultSet.totalrecords; i++) {
    prsLiteral = rt.replace(prsRegex,function (match,varname) {
        return eval(varname + "[" + i + "]");
        // you could instead use return eval(varname) if you're not looping.
    })
    console.log(prsLiteral);
}

In my actual implementation, I choose to use @{{variable}}. One more set of braces. Absurdly unlikely to encounter that unexpectedly. The regex for that would look like /\@\{\{(.*?)(?!\@\{\{)\}\}/g

To make that easier to read

\@\{\{    # opening sequence, @{{ literally.
(.*?)     # capturing the variable name
          # ^ captures only until it reaches the closing sequence
(?!       # negative lookahead, making sure the following
          # ^ pattern is not found ahead of the current character
  \@\{\{  # same as opening sequence, if you change that, change this
)
\}\}      # closing sequence.

If you're not experienced with regex, a pretty safe rule is to escape every non-alphanumeric character, and don't ever needlessly escape letters as many escaped letters have special meaning to virtually all flavors of regex.