eslint-plugin-typescript/docs/rules/member-ordering.md

TypeScript plugin for ESLint

# Require a consistent member declaration order (member-ordering)

A consistent ordering of fields, methods and constructors can make interfaces, type literals, classes and class 
expressions easier to read, navigate and edit.

## Rule Details

This rule aims to standardise the way interfaces, type literals, classes and class expressions are structured.

## Options

This rule, in its default state, does not require any argument, in which case the following order is enforced:          
- `public-static-field`
- `protected-static-field`
- `private-static-field`
- `public-instance-field`
- `protected-instance-field`
- `private-instance-field`
- `public-field` (ignores scope)
- `protected-field` (ignores scope)
- `private-field` (ignores scope)
- `static-field` (ignores accessibility)
- `instance-field` (ignores accessibility)
- `field` (ignores scope and/or accessibility)
- `constructor` (ignores scope and/or accessibility)
- `public-static-method`
- `protected-static-method`
- `private-static-method`
- `public-instance-method`
- `protected-instance-method`
- `private-instance-method`
- `public-method` (ignores scope)
- `protected-method` (ignores scope)
- `private-method` (ignores scope)
- `static-method` (ignores accessibility)
- `instance-method` (ignores accessibility)
- `method` (ignores scope and/or accessibility)

The rule can also take one or more of the following options:
- `default`, use this to change the default order (used when no specific configuration has been provided). 
- `classes`, use this to change the order in classes.
- `classExpressions`, use this to change the order in class expressions.
- `interfaces`, use this to change the order in interfaces.
- `typeLiterals`, use this to change the order in type literals.

### default
Disable using `never` or use one of the following values to specify an order:   
- Fields:   
`public-static-field`   
`protected-static-field`   
`private-static-field`   
`public-instance-field`   
`protected-instance-field`   
`private-instance-field`   
`public-field` (= public-*-field)    
`protected-field` (= protected-*-field)      
`private-field` (= private-*-field)   
`static-field`  (= *-static-field)    
`instance-field` (= *-instance-field)       
`field` (= all)   

- Constructors:  
`public-constructor`  
`protected-constructor`  
`private-constructor`  
`constructor` (= *-constructor)   

- Methods:
`public-static-method`   
`protected-static-method`   
`private-static-method`   
`public-instance-method`   
`protected-instance-method`   
`private-instance-method`   
`public-method` (= public-*-method)     
`protected-method` (= protected-*-method)     
`private-method` (= private-*-method)   
`static-method` (= *-static-method)  
`instance-method` (= *-instance-method)    
`method` (= all)  

Examples of **incorrect** code for the `{ "default": [...] }` option:
```ts
// { "default": ["method", "constructor", "field"] }

interface Foo {
    // -> field
    B: string;
    
    // -> constructor
    new();
    
    // -> method
    A() : void;
}

type Foo = {
    // -> field
    B: string;
    
    // no constructor
    
    // -> method
    A() : void;
}

class Foo {
    // -> * field
    private C: string
    public D: string
    protected static E: string
    
    // -> constructor
    constructor() {}
    
    // -> * method
    public static A(): void {}
    public B(): void {}        
}

const Foo = class {
    // -> * field
    private C: string
    public D: string
    
    // -> constructor
    constructor() {}
    
    // -> * method
    public static A(): void {}
    public B(): void {}
    
    // * field
    protected static E: string
}

// { "default": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals (accessibility and scope are not part of interfaces/type literals)

class Foo {
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}            
}

const Foo = class {
    // private instance field
    private C: string
    
    // -> public static field
    public static E: string
        
    // public instance field    
    public D: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}    
}
```

Examples of **correct** code for the `{ "default": [...] }` option:
```ts
// { "default": ["method", "constructor", "field"] }

interface Foo {
    // -> method
    A() : void;
    
    // -> constructor
    new();
    
    // -> field
    B: string;
}

type Foo = {
    // -> method
    A() : void;
    
    // -> field
    B: string;
}

class Foo {
    // -> * method
    public static A(): void {}
    public B(): void {}
    
    // -> constructor
    constructor() {}
    
    // -> * field
    private C: string
    public D: string
    protected static E: string                
}

const Foo = class {
    // -> * method
    public static A(): void {}
    public B(): void {}
    
    // -> constructor
    constructor() {}
    
    // -> * field
    private C: string
    public D: string
    protected static E: string
}

// { "default": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals (accessibility and scope are not part of interfaces/type literals)

class Foo {
    // -> public instance method
    public B(): void {}
     
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
     
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}                
}

const Foo = class {
    // -> public instance method
    public B(): void {}
    
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> protected static field
    protected static: string
}

// { "default": ["public-static-field", "static-field", "instance-field"] }

// does not apply for interfaces/type literals (accessibility and scope are not part of interfaces/type literals)

class Foo {
    // -> public static field
    public static A: string; 
                   
    // -> * static field
    private static B: string;
    protected statis C:string;
    private static D: string;
    
    // -> * instance field
    private E: string;
}

const foo = class {
    // * method
    public T(): void {}
    
    // -> public static field
    public static A: string; 

    // constructor
    constructor(){}
                   
    // -> * static field
    private static B: string;
    protected statis C:string;
    private static D: string;
    
    // -> * instance field
    private E: string;
}
```

### classes
Disable using `never` or use one of the valid values (see default) to specify an order.  

Examples of **incorrect** code for the `{ "classes": [...] }` option:
```ts
// { "classes": ["method", "constructor", "field"] }

// does not apply for interfaces/type literals/class expressions.

class Foo {
    // -> field
    private C: string
    public D: string
    protected static E: string
    
    // -> constructor
    constructor() {}
    
    // -> method
    public static A(): void {}
    public B(): void {}        
}

// { "classes": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals/class expressions.

class Foo {
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}            
}
```

Examples of **correct** code for `{ "classes": [...] }` option:
```ts
// { "classes": ["method", "constructor", "field"] }

// does not apply for interfaces/type literals/class expressions.

class Foo {
    // -> * method
    public static A(): void {}
    public B(): void {}
    
    // -> constructor
    constructor() {}
    
    // -> * field
    private C: string
    public D: string
    protected static E: string                
}

// { "classes": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals/class expressions.

class Foo {
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}            
}
```

### classExpressions
Disable using `never` or use one of the valid values (see default) to specify an order.   

Examples of **incorrect** code for the `{ "classExpressions": [...] }` option:
```ts
// { "classExpressions": ["method", "constructor", "field"] }

// does not apply for interfaces/type literals/class expressions.

const foo = class {
    // -> field
    private C: string
    public D: string
    protected static E: string
    
    // -> constructor
    constructor() {}
    
    // -> method
    public static A(): void {}
    public B(): void {}        
}

// { "classExpressions": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals/class expressions.

const foo = class {
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}            
}
```

Examples of **correct** code for `{ "classExpressions": [...] }` option:
```ts
// { "classExpressions": ["method", "constructor", "field"] }

// does not apply for interfaces/type literals/class expressions.

const foo = class {
    // -> * method
    public static A(): void {}
    public B(): void {}
    
    // -> constructor
    constructor() {}
    
    // -> * field
    private C: string
    public D: string
    protected static E: string                
}

// { "classExpressions": ["public-instance-method", "public-static-field"] }

// does not apply for interfaces/type literals/class expressions.

const foo = class {
    // private instance field
    private C: string
    
    // public instance field
    public D: string
    
    // -> public static field
    public static E: string
    
    // constructor
    constructor() {}
    
    // public static method
    public static A(): void {}
    
    // -> public instance method
    public B(): void {}            
}
```

### interfaces
Disable using `never` or use one of the following values to specify an order:   
`field`   
`constructor`     
`method`   

Examples of **incorrect** code for the `{ "interfaces": [...] }` option:
```ts
// { "interfaces": ["method", "constructor", "field"] }

// does not apply for classes/class expressions/type literals

interface Foo {
    // -> field
    B: string;
    
    // -> constructor
    new();
    
    // -> method
    A() : void;
}
```

Examples of **correct** code for the `{ "interfaces": [...] }` option:
```ts
// { "interfaces": ["method", "constructor", "field"] }
 
// does not apply for classes/class expressions/type literals
 
interface Foo {
    // -> method
    A() : void;
         
    // -> constructor
    new();     
    
    // -> field
    B: string;
}
```

### typeLiterals
Disable using `never` or use one of the valid values (see interfaces) to specify an order.  
   
Examples of **incorrect** code for the `{ "typeLiterals": [...] }` option:
```ts
// { "typeLiterals": ["method", "constructor", "field"] }

// does not apply for classes/class expressions/interfaces

type Foo = {
    // -> field
    B: string;
    
    // -> method
    A() : void;
}
```

Examples of **correct** code for the `{ "typeLiterals": [...] }` option:
```ts
// { "typeLiterals": ["method", "constructor", "field"] }
 
// does not apply for classes/class expressions/interfaces
 
type Foo = {
    // -> method
    A() : void;
         
    // -> constructor
    new();     
    
    // -> field
    B: string;
}
```

## When Not To Use It

If you don't care about the general structure of your classes and interfaces, then you will not need this rule.

## Compatibility

* TSLint: [member-ordering](https://palantir.github.io/tslint/rules/member-ordering/)