Best practices for Typescript coding

Coding standards are basically a few sets of guidelines or programming styles to be followed while writing the source code of any application. Almost all the software companies follow these basic set of guidelines to have a well defined code.

So let’s get started…

1. Limit the length of code to 500–600 lines in a file and the methods to 20–30 lines.
2. Naming convention of variable/method/class names:

• Variable Names: camelCase
  Example:
  firstNumber = 12
• Constants: UPPER_CASE with underscore ‘_’ between multiple words
  Example:
  const FIRST_NUMBER = 18
• Method Names: camelCase
  Example:
  sumOfTwoNumbers()
• Class Names: PascalCase
  Example:
  export class EmployeeDetails {}
• File Names: lower-case (Separated by ‘-’ if the name is of two/more words)
  Example:
  employee-details

3. Mention data types of variables while declaration and for method parameters.

• Variable Type
  Example:
  firstNumber: number
• Parameter Type
  Example:

Data types for method parameters

4. Avoid the use of type ‘any’. Create an interface/class instead.
Example:
Let’s assume that we need to assign the details of a person to a particular variable. So, we create a variable user of type UserDetails as shown below:
user: UserDetails

UserDetails Interface

Interface for UserDetails

5. Add method documentation for methods as well as parameters passed (Press /** + enter wherever method documentation needs to be added)
Example:

Method documentation

6. Keep method/variable names as informative as possible.

• Method Name
  Example:

Informative method name

• Variable Name
  Example:
  firstName: string

7. Use data access specifiers while declaring variables/methods (Like public/private etc)
Example:
If we declare a variable ‘firstNumber’ and it is used only inside the class say ‘Addition’, it is marked as private.
private firstNumber: number

Similarly, a method can be marked as private if it is only used inside a particular class.
private sumOfTwoNumbers(): number {}

However, If a variable is used in an HTML file, it should be marked public.

8. Use TSLint and make sure not to disable any lint rule. TSLint extension should be enabled in order to include lint rules in the project.

9. Scope of the variables should be as minimum as possible.
Example:
Since FIRST_NUMBER is used only inside the method sumOfTwoNumber, it is initialised inside that particular method, thus limiting the scope of the variable to that particular method.

Scope of FIRST_NUMBER

10. Avoid using repetitive if else (Use switch case instead)
Example:

Switch case

11. Use try catch to handle the error and exceptions. Make sure there is no unhandled exception in your code.
Example:

Try catch block for error handling

12. Always log the errors and relevant information. This helps in debugging the code in case of errors. The following log levels can be used to add logging in your code:

• Error
  Example:
  console.error('This is an error log')
• Warn
  Example:
  console.warn('This is an warning log')
• Info
  Example:
  console.info('This is an info log')
• Debug
  Example:
  console.debug('This is a debug log')
• Trace
  Example:
  console.trace('This is a trace log')

13. Add TODOs for pending code blocks.
Example:

TODO for pending code block

14. Reuse the code as much as possible and remove unnecessary code blocks.

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Keep Coding!!