Is there a better way to do optional function parameters in JavaScript? [duplicate]

Answer 1

I am used to seeing a few basic variations on handling optional variables. Sometimes, the relaxed versions are useful.

function foo(a, b, c) {
  a = a || "default";   // Matches 0, "", null, undefined, NaN, false.
  a || (a = "default"); // Matches 0, "", null, undefined, NaN, false.

  if (b == null) { b = "default"; } // Matches null, undefined.

  if (typeof c === "undefined") { c = "default"; } // Matches undefined.
}

The falsy default used with variable a is, for example, used extensively in Backbone.js.