npm install
npm test

Follow the TDD rules:

• You can't write any production code until you have first written a failing unit test.
• You can't write more of a unit test than is sufficient to fail, and not compiling is failing.
• You can't write more production code than is sufficient to pass the currently failing unit test.

Follow the RGR cycle.

• Red - create a unit test that fails.
• Green - Write code that makes the test pass.
• Refactor - Clean up the mess you just made.

With the actual tests described below, try to not read ahead. Focus on the above and not on the final code.

Count(null) ==> returns 0

Count(" \n\n\t\r ") ==> returns 0

Count("Hello") ==> returns 1

Count("Hello world") ==> returns 2

Count("  \nHello  \r ") ==> returns 1

Count("Hello crazy \n  world") ==> returns 3

Count("Hello world in world") ==> returns 3

Count("Hello world hello") ==> returns 2

Count("Hello world hello.") ==> returns 2

Count("Hello (world) - 123.") ==> returns 3

Count("Allô? Allo est la fin.") ==> returns 4