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     let v;
  17     if (key == "") {
  18       if (curindex == -1)
  19         throw Error("Cannot mix named and positional indices in string formatting.");
  20
  21       if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
  22         v = d;
  23       }
  24       else if (!(curindex in d))
  25         throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
  26       else {
  27         v = d[curindex];
  28       }
  29
  30       ++curindex;
  31     }
  32     else {
  33       key = key.slice(1, -1);
  34       if (curindex > 0)
  35         throw Error("Cannot mix named and positional indices in string formatting.");
  36       curindex = -1;
  37
  38       if (!(key in d))
  39         throw Error("Key '%s' not present during string substitution.".format(key));
  40       v = d[key];
  41     }
  42     switch (type) {
  43     case "s":
  44       if (v === undefined)
  45         return "<undefined>";
  46       return v.toString();
  47     case "r":
  48       return uneval(v);
  49     case "i":
  50       return parseInt(v);
  51     case "f":
  52       return Number(v);
  53     case "%":
  54       return "%";
  55     default:
  56       throw Error("Unexpected format character '%s'.".format(type));
  57     }
  58   }
  59   return this.replace(/%(\([^)]+\))?(.)/g, r);
  60 };