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no-use-before-define

Disallow the use of variables before they are defined.

🧱

This is an "extension" rule that replaces a core ESLint rule to work with TypeScript. See Rules > Extension Rules.

This rule extends the base no-use-before-define rule from ESLint core. 它增加了对 type、interface 和 enum 声明的支持。

¥It adds support for type, interface and enum declarations.

如何使用​

eslint.config.mjs
export default tseslint.config({
  rules: {
    // Note: you must disable the base rule as it can report incorrect errors
    "no-use-before-define": "off",
    "@typescript-eslint/no-use-before-define": "error"
  }
});

在线运行试试这个规则 ↗

选项​

See eslint/no-use-before-define's options.

¥Options

该规则添加了以下选项：

¥This rule adds the following options:

interface Options extends BaseNoUseBeforeDefineOptions {
  enums?: boolean;
  typedefs?: boolean;
  ignoreTypeReferences?: boolean;
}

const defaultOptions: Options = {
  ...baseNoUseBeforeDefineDefaultOptions,
  enums: true,
  typedefs: true,
  ignoreTypeReferences: true,
};

enums​

Whether to check references to enums. Default: true.

如果这是 true，则此规则会在枚举声明之前对枚举的每个引用发出警告。如果这是 false，则当引用在子范围内时，此规则将忽略对枚举的引用。

¥If this is true, this rule warns every reference to a enum before the enum declaration. If this is false, this rule will ignore references to enums, when the reference is in a child scope.

{ "enums": true } 选项的代码示例：

¥Examples of code for the { "enums": true } option:

const x = Foo.FOO;

enum Foo {
  FOO,
}
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typedefs​

Whether to check references to types. Default: true.

如果这是 true，则此规则会在类型声明之前对类型的每个引用发出警告。如果这是 false，则此规则将忽略对类型的引用。

¥If this is true, this rule warns every reference to a type before the type declaration. If this is false, this rule will ignore references to types.

{ "typedefs": false } 选项的正确代码示例：

¥Examples of correct code for the { "typedefs": false } option:

let myVar: StringOrNumber;
type StringOrNumber = string | number;
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ignoreTypeReferences​

Whether to ignore type references, such as in type annotations and assertions. Default: true.

如果这是 true，则此规则将忽略所有类型引用。如果这是 false，这将检查所有类型引用。

¥If this is true, this rule ignores all type references. If this is false, this will check all type references.

{ "ignoreTypeReferences": true } 选项的正确代码示例：

¥Examples of correct code for the { "ignoreTypeReferences": true } option:

let var1: StringOrNumber;
type StringOrNumber = string | number;

let var2: Enum;
enum Enum {}
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'## 资源'

Taken with ❤️ from ESLint core.