1 files changed, 65 insertions, 0 deletions
diff --git a/config/string-format.js b/config/string-format.js
new file mode 100644
index 000000000..7319eb859
--- /dev/null
+++ b/config/string-format.js
@@ -0,0 +1,65 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+String.prototype.format = function string_format() {
+  // there are two modes of operation... unnamed indices are read in order;
+  // named indices using %(name)s. The two styles cannot be mixed.
+  // Unnamed indices can be passed as either a single argument to this function,
+  // multiple arguments to this function, or as a single array argument
+  let curindex = 0;
+  let d;
+
+  if (arguments.length > 1) {
+    d = arguments;
+  }
+  else
+    d = arguments[0];
+
+  function r(s, key, type) {
+    if (type == '%')
+      return '%';
+    
+    let v;
+    if (key == "") {
+      if (curindex == -1)
+        throw Error("Cannot mix named and positional indices in string formatting.");
+
+      if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
+        v = d;
+      }
+      else if (!(curindex in d))
+        throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
+      else {
+        v = d[curindex];
+      }
+
+      ++curindex;
+    }
+    else {
+      key = key.slice(1, -1);
+      if (curindex > 0)
+        throw Error("Cannot mix named and positional indices in string formatting.");
+      curindex = -1;
+
+      if (!(key in d))
+        throw Error("Key '%s' not present during string substitution.".format(key));
+      v = d[key];
+    }
+    switch (type) {
+    case "s":
+      if (v === undefined)
+        return "<undefined>";
+      return v.toString();
+    case "r":
+      return uneval(v);
+    case "i":
+      return parseInt(v);
+    case "f":
+      return Number(v);
+    default:
+      throw Error("Unexpected format character '%s'.".format(type));
+    }
+  }
+  return this.replace(/%(\([^)]+\))?(.)/g, r);
+};