Simplify interpolate() function in demo script

www/js/demo/it.js

@@ -5,29 +5,11 @@ function addScript(url) {
 }
 
 function interpolate(str, params) {
-    var returnStr = "";
     try {
-        var charArray = Array.from(str);
+        return eval(`env => { with (env) { return \`${str}\` } }`)(params)
-        while (charArray.length > 0) {
-            var current = charArray.shift();
-            if (current === "$" && charArray[0] === "{") {
-                var evalStr = "(function(env) { with(env) { return "
-                charArray.shift();
-                while (charArray.length > 0 && charArray[0] !== "}") {
-                    evalStr += charArray.shift()
-                }
-                charArray.shift();
-                evalStr += " } })";
-                // console.log("Evaling", evalStr);
-                returnStr += eval(evalStr)(params);
-            } else {
-                returnStr += current;
-            }
-        }
     } catch (e) {
-        returnStr = e.message;
+        return e.message;
     }
-    return returnStr;
 }
 
 function initMockRequests() {