var number = 15;

switch(number) {

case 5:

console.log(‘number is 5’);

break;

case 10:

console.log(‘number is 10’);

break;

case 15:

console.log(‘number is 15’);

}

Looking at the above code, there’s a lot of new syntax to analyse here, so let’s work our way from top to bottom.

• We start with the keyword switch followed by parenthesis.
• Inside the parenthesis we enter our expression. (The expression is the value that we want to evaluate our cases against. So in this case we just enter the variable number. This means that every case inside the switch statement will be evaluated against the number 15.)
• Then we move down to the case keyword followed by the test case, so in the first example we are using ‘case 5’. This is saying: ‘if the number is 5 then this case is true.’
• This is followed by a colon, not a semi-colon, which is something we have only seen before in objects.
• Then on a new line we enter our code that we want to run when the case is true.
• After we finish writing our code, we follow it up with a break keyword followed by a semi-colon. The break keyword instructs JavaScript to ‘break’ out of the switch block and stop the execution of any more code inside the switch statement.
• After our break keyword, we can write another case directly below, with the same syntax.

During execution of the code, JavaScript will handle the switch statement very much like an if else statement. It will look for a single valid condition that returns TRUE, execute that code, then move on to the next section of your code outside of the statement.

You will notice that the final case in the switch statement doesn’t contain a break. This is because the code will stop here anyway, as this is not a loop, and as soon as JavaScript has worked its way through your statement, it will move on, even if it doesn’t find a match.

In the current state of our switch statement, it is entirely possible for there to be no matches, and therefore no code is executed. If we want to emulate the else functionality of an if statement, and mitigate against a situation where no matches are found, we can make use of the default keyword. The default keyword is largely identical to the else section of an if statement, in that it is run if no other match is found.

To use the default keyword, we simply add it into our switch statement, like so: