no-use-before-define
Disallow the use of variables before they are defined.
This rule extends the base eslint/no-use-before-define rule.
It adds support for type, interface and enum declarations.
How to Use
- Flat Config
- Legacy Config
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"
}
});
module.exports = {
"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"
}
};
Try this rule in the playground ↗
Options
See eslint/no-use-before-define's options.
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.
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.
Examples of code for the { "enums": true } option:
- ❌ Incorrect
- ✅ Correct
const x = Foo.FOO;
enum Foo {
FOO,
}
function foo() {
return Foo.FOO;
}
enum Foo {
FOO,
}
typedefs
Whether to check references to types. Default: true.
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.
Examples of correct code for the { "typedefs": false } option:
let myVar: StringOrNumber;
type StringOrNumber = string | number;
ignoreTypeReferences
Whether to ignore type references, such as in type annotations and assertions. Default: true.
If this is true, this rule ignores all type references.
If this is false, this will check all type references.
Examples of correct code for the { "ignoreTypeReferences": true } option:
let var1: StringOrNumber;
type StringOrNumber = string | number;
let var2: Enum;
enum Enum {}