Conditionals

lesson_6.md

Conditionals

As we have seen, everything in JavaScript will be either true or false, we can use this to direct the flow of our application.

    if (something is true) {
        // Do thing
    }

In the above example, the thing will only be executed if something is truthy. If it is falsey it will skip that part of the code.

When determining if something is truthy, let's look at some operators we can use:

OPERATOR	EXPLAINATION
===	Is equal to
!==	Is not equal to
>=	Is greater than or equal to
>	Is greater than
<=	Is less than or equal to
<	Is less than

Let's look at a real example.

    let balance = 100
    if (balance <= 0) {
        // Do something when a users balance is negative
    } else if (balance === 0) {
        // Do something if the balance is 0
    } else {
        // Do something if the balance is positive
    }

When we use these conditional operators, we do not test if the value of balance itself is truthy or falsey, but instead if the result of balance when run on these operators is truthy or falsey. E.g When balance is 0, balance is falsey, but balance === 0 is truthy

Anatomy of If/Else If/Else

The three keywords here are:

• if
• else if
• else

You can simply just have an if block and nothing else, you can also have if...else with no else if.

If you just use if on its own, be aware that when it is true and the block inside the if condition is run, when there is no else it will carry on at the same point as a condition where it was false.

For example you would want to avoid the following:

    if(balance < 0) {
        console.log('You have a NEGATIVE balance!!);
    }
    
    console.log('You have a POSITIVE balance');

In this example, if the balance was less than 0, then BOTH console logs would be printed.