JavaScript - Expand variables in string

expandVars.js

// Polyfill to expand variables in a string

// Example: "Welcome back ${name}. Glad to see you".expandVars({name: "Fred"});
// Variables defined in `vars` can be string/number values or a getter function.
// eslint-disable-next-line no-extend-native
String.prototype.expandVars = function(vars) {
  return this.replace(/\${([^{}]*)}/g, function(str, varName) {
    var value = vars[varName];
    return typeof value === "string" || typeof value === "number" ? value : str;
  });
};