type-annotation-spacing
Spacing around type annotations improves the readability of the code. Although the most commonly used style guideline for type annotations in TypeScript prescribes adding a space after the colon, but not before it, it is subjective to the preferences of a project. For example:
// with space after, but not before (default if no option is specified)
let foo: string = "bar";
// with no spaces
let foo:string = "bar";
// with space before and after
let foo : string = "bar";
// with space before, but not after
let foo :string = "bar";
// with spaces before and after the fat arrow (default if no option is specified)
type Foo = (string: name) => string;
// with no spaces between the fat arrow
type Foo = (string: name)=>string;
// with space after, but not before the fat arrow
type Foo = (string: name)=> string;
// with space before, but not after the fat arrow
type Foo = (string: name) =>string;Examples
This rule aims to enforce specific spacing patterns around type annotations and function types in type literals.
/*eslint @stylistic/ts/type-annotation-spacing: "error"*/
let foo:string = "bar";
let foo :string = "bar";
let foo : string = "bar";
function foo():string {}
function foo() :string {}
function foo() : string {}
class Foo {
name:string;
}
class Foo {
name :string;
}
class Foo {
name : string;
}
type Foo = ()=>{};
type Foo = () =>{};
type Foo = ()=> {};/*eslint @stylistic/ts/type-annotation-spacing: "error"*/
let foo: string = "bar";
function foo(): string {}
class Foo {
name: string;
}
type Foo = () => {};Options
after
Examples of incorrect code for this rule with the { "before": false, "after": true } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": true }]*/
let foo:string = "bar";
let foo :string = "bar";
let foo : string = "bar";
function foo():string {}
function foo() :string {}
function foo() : string {}
class Foo {
name:string;
}
class Foo {
name :string;
}
class Foo {
name : string;
}
type Foo = ()=>{};
type Foo = () =>{};
type Foo = () => {};Examples of correct code for this rule with the { "before": false, "after": true } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": true }]*/
let foo: string = "bar";
function foo(): string {}
class Foo {
name: string;
}
type Foo = ()=> {};before
Examples of incorrect code for this rule with the { "before": true, "after": true } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": true, "after": true }]*/
let foo: string = "bar";
let foo:string = "bar";
let foo :string = "bar";
function foo(): string {}
function foo():string {}
function foo() :string {}
class Foo {
name: string;
}
class Foo {
name:string;
}
class Foo {
name :string;
}
type Foo = ()=>{};
type Foo = () =>{};
type Foo = ()=> {};Examples of correct code for this rule with the { "before": true, "after": true } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": true, "after": true }]*/
let foo : string = "bar";
function foo() : string {}
class Foo {
name : string;
}
type Foo = () => {};overrides - colon
Examples of incorrect code for this rule with the { "before": false, "after": false, "overrides": { "colon": { "before": true, "after": true } } } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": false, "overrides": { "colon": { "before": true, "after": true } } }]*/
let foo: string = "bar";
let foo:string = "bar";
let foo :string = "bar";
function foo(): string {}
function foo():string {}
function foo() :string {}
class Foo {
name: string;
}
class Foo {
name:string;
}
class Foo {
name :string;
}
type Foo = () =>{};
type Foo = ()=> {};
type Foo = () => {};Examples of correct code for this rule with the { "before": false, "after": false, "overrides": { "colon": { "before": true, "after": true } } } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": false, "overrides": { "colon": { "before": true, "after": true } } }]*/
let foo : string = "bar";
function foo() : string {}
class Foo {
name : string;
}
type Foo = {
name: (name : string)=>string;
}
type Foo = ()=>{};overrides - arrow
Examples of incorrect code for this rule with the { "before": false, "after": false, "overrides": { "arrow": { "before": true, "after": true } } } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": false, "overrides": { "arrow": { "before": true, "after": true } } }]*/
let foo: string = "bar";
let foo : string = "bar";
let foo :string = "bar";
function foo(): string {}
function foo():string {}
function foo() :string {}
class Foo {
name: string;
}
class Foo {
name : string;
}
class Foo {
name :string;
}
type Foo = ()=>{};
type Foo = () =>{};
type Foo = ()=> {};Examples of correct code for this rule with the { "before": false, "after": false, "overrides": { "arrow": { "before": true, "after": true } } } option:
/*eslint @stylistic/ts/type-annotation-spacing: ["error", { "before": false, "after": false, "overrides": { "arrow": { "before": true, "after": true } } }]*/
let foo:string = "bar";
function foo():string {}
class Foo {
name:string;
}
type Foo = () => {};When Not To Use It
If you don't want to enforce spacing for your type annotations, you can safely turn this rule off.