Clean Code - Functions

Clean Functions

Function Should Be Small

If you think your function is small, you can make it even smaller

Warning

A function should do a single thing. If it does more than one thing-refactor it into a context.

Blocks within if - else or while statements should be one line long for readability. It should be a function call or a return statement.

// write
const hasStudents: boolean = myArray.length > 0
function assignStudents(students: Student[]) {
	// ...
}
 
if(hasStudents) {
	assignStudents(myArray);
}

Functions Should Operate on One Abstraction Level

If you can extract a meaningful function from another one, this concept is violated

Take MVC

→ A model class or function should have no DOM access. → A view should have nothing to do with data manipulation

Functions Should Read Like ‘to’ - Paragraphs

Start with 'to'

Try and describe every function with a to - prefix. When a to-paragraph ends, open a new scope below the previous

This is an example from my Crawley app between different levels of abstraction

• To Crawl observed items, we must retrieve them from the database, then we crawl their current values. Finally, we return them to the user
  • To crawl observed items, we must iterate through them, crawl the current content, add its value to our history table and return the value
    • To crawl the current content of a single observed item, we make an http request, query the value of the item and return it
    • To add a value to the history table, we take the value of the crawled item and write it into the SQL table

Try and Avoid Switch Statements

If it’s necessary, use with caution and at the lowest level of abstraction

Descriptive Names

See Naming functions

Function Arguments

• Should be 0
• Can be 1 or 2
• Should rarely be 3
• Never me more than that

Don’t pass flags (true - false) into arguments