When the code runs into an unexpected problem, the JavaScript idiomatic way to handle this situation is through exceptions.

An exception is created using the throw keyword:

throw value

where value can be any JavaScript value including a string, a number or an object.

As soon as JavaScript executes this line, the normal program flow is halted and the control is held back to the nearest exception handler.

Example:

const test = (param) => {
  if (typeof param !== 'number') {
    throw 'The param should be a number!'
  }
}

test('test')

Lessons in this unit: