default-param-last

Enforce default parameters to be last

Putting default parameter at last allows function calls to omit optional tail arguments.

// Correct: optional argument can be omitted function createUser(id, isAdmin = false) {} createUser("tabby") // Incorrect: optional argument can **not** be omitted function createUser(isAdmin = false, id) {} createUser(undefined, "tabby") 
1
2
3
4
5
6
7

Rule Details

This rule enforces default parameters to be the last of parameters.

Examples of incorrect code for this rule:

/* eslint default-param-last: ["error"] */ function f(a = 0, b) {} function g(a, b = 0, c) {} 
1
2
3
4
5

Examples of correct code for this rule:

/* eslint default-param-last: ["error"] */ function f(a, b = 0) {} function g(a, b = 0, c = 0) {} 
1
2
3
4
5

This rule additionally supports TypeScript type syntax.

Examples of incorrect TypeScript code for this rule:

/* eslint default-param-last: ["error"] */ function h(a = 0, b: number) {} 
1
2
3

Examples of correct TypeScript code for this rule:

/* eslint default-param-last: ["error"] */ function h(a = 0, b?: number) {} 
1
2
3

Options

This rule has no options.

Version

This rule was introduced in ESLint v6.4.0.

Resources

• Rule source
• Tests source