michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: String.prototype.format = function string_format() {
michael@0:   // there are two modes of operation... unnamed indices are read in order;
michael@0:   // named indices using %(name)s. The two styles cannot be mixed.
michael@0:   // Unnamed indices can be passed as either a single argument to this function,
michael@0:   // multiple arguments to this function, or as a single array argument
michael@0:   let curindex = 0;
michael@0:   let d;
michael@0: 
michael@0:   if (arguments.length > 1) {
michael@0:     d = arguments;
michael@0:   }
michael@0:   else
michael@0:     d = arguments[0];
michael@0: 
michael@0:   function r(s, key, type) {
michael@0:     if (type == '%')
michael@0:       return '%';
michael@0:     
michael@0:     let v;
michael@0:     if (key == "") {
michael@0:       if (curindex == -1)
michael@0:         throw Error("Cannot mix named and positional indices in string formatting.");
michael@0: 
michael@0:       if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
michael@0:         v = d;
michael@0:       }
michael@0:       else if (!(curindex in d))
michael@0:         throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
michael@0:       else {
michael@0:         v = d[curindex];
michael@0:       }
michael@0: 
michael@0:       ++curindex;
michael@0:     }
michael@0:     else {
michael@0:       key = key.slice(1, -1);
michael@0:       if (curindex > 0)
michael@0:         throw Error("Cannot mix named and positional indices in string formatting.");
michael@0:       curindex = -1;
michael@0: 
michael@0:       if (!(key in d))
michael@0:         throw Error("Key '%s' not present during string substitution.".format(key));
michael@0:       v = d[key];
michael@0:     }
michael@0:     switch (type) {
michael@0:     case "s":
michael@0:       if (v === undefined)
michael@0:         return "<undefined>";
michael@0:       return v.toString();
michael@0:     case "r":
michael@0:       return uneval(v);
michael@0:     case "i":
michael@0:       return parseInt(v);
michael@0:     case "f":
michael@0:       return Number(v);
michael@0:     default:
michael@0:       throw Error("Unexpected format character '%s'.".format(type));
michael@0:     }
michael@0:   }
michael@0:   return this.replace(/%(\([^)]+\))?(.)/g, r);
michael@0: };