Replace multiple if statements with a single switch statement

We demonstrate the trick with a simple issue: Determine the quarter of a given date. Since the month in JavaScript is zero-based, the month of a given `date` can be determined as

// `date` is the input date
const month = date.getMonth() + 1;

The quarter is calculated based on the range of month:

let quarter = 1;
if (month <= 3) {
    quarter = 1;
} else if (month <= 6) {
    quarter = 2;
} else if (month <= 9) {
    quarter = 3;
} else {
    quarter = 4;
}

It is not easy for us to scan multiple `if` statements above. We can make it more readable with a single `switch (true)` statement:

switch (true) {
    case month <= 3:
        quarter = 1;
        break;
    case month <= 6:
        quarter = 2;
        break;
    case month <= 9:
        quarter = 3;
        break;
    default:
        quarter = 4;
        break;
}

This trick gives us an idea of using `switch (true)` to make the code more readable. The specific issue in this post, calculating the quarter of a given date, can be done with a single line-of-code.

Replace multiple if statements with a single switch statement

See also