Global footprint

If you are developing a module, which might be running on a web page, which also runs other modules, then you must beware the variable name overlapping.

Suppose we are developing a counter module:

  1. var myCounter = {
  2.   number: 0,
  3.   plusPlus: function () {
  4.     this.number = this.number + 1;
  5.   },
  6.   isGreaterThanTen: function () {
  7.     return this.number > 10;
  8.   },
  9. };

Note: this technique is often used with closures, to make the internal state immutable from the outside.

The module now takes only one variable name — myCounter. If any other module on the page makes use of such names like number or isGreaterThanTen then it’s perfectly safe, because we will not override each others values;