xpcom/analysis/string-format.js

   1 String.prototype.format = function string_format() {
   2   // there are two modes of operation... unnamed indices are read in order;
   3   // named indices using %(name)s. The two styles cannot be mixed.
   4   // Unnamed indices can be passed as either a single argument to this function,
   5   // multiple arguments to this function, or as a single array argument
   6   let curindex = 0;
   7   let d;
   8
   9   if (arguments.length > 1) {
  10     d = arguments;
  11   }
  12   else
  13     d = arguments[0];
  14
  15   function r(s, key, type) {
  16     if (type == '%')
  17       return '%';
  18
  19     let v;
  20     if (key == "") {
  21       if (curindex == -1)
  22         throw Error("Cannot mix named and positional indices in string formatting.");
  23
  24       if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
  25         v = d;
  26       }
  27       else if (!(curindex in d))
  28         throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
  29       else {
  30         v = d[curindex];
  31       }
  32
  33       ++curindex;
  34     }
  35     else {
  36       key = key.slice(1, -1);
  37       if (curindex > 0)
  38         throw Error("Cannot mix named and positional indices in string formatting.");
  39       curindex = -1;
  40
  41       if (!(key in d))
  42         throw Error("Key '%s' not present during string substitution.".format(key));
  43       v = d[key];
  44     }
  45     switch (type) {
  46     case "s":
  47       if (v === undefined)
  48         return "<undefined>";
  49       return v.toString();
  50     case "r":
  51       return uneval(v);
  52     case "i":
  53       return parseInt(v);
  54     case "f":
  55       return Number(v);
  56     default:
  57       throw Error("Unexpected format character '%s'.".format(type));
  58     }
  59   }
  60   return this.replace(/%(\([^)]+\))?(.)/g, r);
  61 };