How to perform case-insensitive sorting in JavaScript?

In (almost :) a one-liner

["Foo", "bar"].sort(function (a, b) {
    return a.toLowerCase().localeCompare(b.toLowerCase());
});

Which results in

[ 'bar', 'Foo' ]

While

["Foo", "bar"].sort();

results in

[ 'Foo', 'bar' ]

myArray.sort(
  function(a, b) {
    if (a.toLowerCase() < b.toLowerCase()) return -1;
    if (a.toLowerCase() > b.toLowerCase()) return 1;
    return 0;
  }
);

EDIT: Please note that I originally wrote this to illustrate the technique rather than having performance in mind. Please also refer to answer @Ivan Krechetov for a more compact solution.

It is time to revisit this old question.

You should not use solutions relying on toLowerCase. They are inefficient and simply don't work in some languages (Turkish for instance). Prefer this:

['Foo', 'bar'].sort((a, b) => a.localeCompare(b, undefined, {sensitivity: 'base'}))

Check the documentation for browser compatibility and all there is to know about the sensitivity option.