The throw statement allows you to generate a custom error (throw an exception), which can be a String, a Number, a Boolean, or an Object.

<!-- html element to place output -->
<p id="my_output"></p>

In the following, we use x as our value (let’s say it was input by the user in a form field). The user was asked to input a number between 1 and 5.

We then use the throw statement to look for errors (try) and output them (catch) to the html element.

If no errors are found, nothing will be output using the “catch”, and the code will continue to run after line 13.

// variable
let x = 13;

// throw statement
try {
    if(x == '')  throw 'You did not enter a value.';
    if(isNaN(x)) throw 'You did not enter a number.';
    if(x > 5)   throw 'The number entered is too high.';
    if(x < 1)  throw 'The number entered is too low.';
  }
catch(err) {
    document.getElementById('my_output').innerHTML = err;
  }

The number entered is too high.

condition throw 'message';