Early return
Written byPhuoc Nguyen
Created
21 Mar, 2021
Category
Practice
Tags
JavaScript
Using the
`if` statement is a common technique to deal with conditional logics. The code flow is split into different branches based on a given logic.Let's take a look at a simple function that suffixes a given hour number with am or pm. The suffix is determined based on which range the hour belongs to as you can see in the following table:
| Hour | With suffix |
|---|---|
| 0 | 12am |
| 1 - 11 | 1am - 11am |
| 12 | 12pm |
| 13 - 23 | 1pm - 11pm |
An initial implementation of the function could look like:
js
const suffixAmPm = (hour) => {
if (hour === 0) {
return '12am';
} else {
if (hour < 12) {
return `${hour}am`;
} else {
if (hour === 12) {
return '12pm';
} else {
return `${hour % 12}pm`;
}
}
}
};Imagine how the code looks like if we use multiple nested
`if` statements. It's very hard to follow and maintain. Rather than using `else` or nested `if` statements, the function can return as soon as the condition matches:js
const fn = (args) => {
if (condition) {
return 'foo';
} else {
// Long implementation
return 'bar';
}
};
// Better
const fn = (args) => {
if (condition) {
return 'foo';
}
// Long implementation
// Don't need to wrap within an `else`
return 'bar';
};Using this practice, a new version of the
`suffixAmPm` function looks like:js
const suffixAmPm = (hour) => {
if (hour === 0) {
return '12am';
}
if (hour < 12) {
return `${hour}am`;
}
if (hour === 12) {
return '12pm';
}
return `${hour % 12}pm`;
};#See also
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Phước Nguyễn