generateTemplateString.js

/**
 * Produces a function which uses template strings to do simple interpolation from objects.
 * 
 * Usage:
 *    var makeMeKing = generateTemplateString('${name} is now the king of ${country}!');
 * 
 *    console.log(makeMeKing({ name: 'Bryan', country: 'Scotland'}));
 *    // Logs 'Bryan is now the king of Scotland!'
 */
var generateTemplateString = (function(){
    var cache = {};

    function generateTemplate(template){

    var fn = cache[template];

    if (!fn){
        
    // Replace ${expressions} (etc) with ${map.expressions}.

    var sanitized = template
        .replace(/\$\{([\s]*[^;\s\{]+[\s]*)\}/g, function(_, match){
            return `\$\{map.${match.trim()}\}`;
            })
        // Afterwards, replace anything that's not ${map.expressions}' (etc) with a blank string.
        .replace(/(\$\{(?!map\.)[^}]+\})/g, '');
    
    fn = Function('map', `return \`${sanitized}\``);

    }

    return fn;
};

return generateTemplate;
})();

A function which converts a regular string to a function, accepting a map of values to interpolate. Allows dynamic template string creation.

Hm. And what about: fs.readFile('views/template.somelanguageorhtml','utf-8', function(err, data){
var d= generateTemplateString(data); console.log(d({ name: 'Bryan', country:'Russia'}));
}) ? Can I or somebody else make like this, say, from a read file or from fs.createReadStream?

there is an error in your function :

var test = generateTemplateString('/api/${param1}/${param2}/')
console.log(test({param1: 'bar', param2: 'foo'})) // /api/bar//

Fixed. Thanks for the help.

It seems to me that cache is being checked, but never assigned to? Perhaps add cache[template] = fn on line 29.

I've modified your gist to support cache, and rewritten it to an es6 module. See the performance gain on jsPerf.