eslint/no-shadow Suspicious
What it does
Disallows variable declarations from shadowing variables declared in the outer scope.
Why is this bad?
Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. This can cause confusion, as it may be unclear which variable is being referenced, and can lead to bugs that are difficult to diagnose.
Examples
Examples of incorrect code for this rule:
var x = 1;
function foo() {
var x = 2; // x shadows the outer x
}Examples of correct code for this rule:
var x = 1;
function foo() {
var y = 2; // different name, no shadowing
}Configuration
This rule accepts a configuration object with the following properties:
allow
type: string[]
default: []
List of variable names that are allowed to shadow.
builtinGlobals
type: boolean
default: false
Whether to report shadowing of built-in global variables.
hoist
type: "all" | "functions" | "functions-and-types" | "never" | "types"
default: "functions-and-types"
Controls how hoisting is handled when checking for shadowing.
"all"
Report shadowing even before the outer variable is declared (due to hoisting).
"functions"
Only report shadowing for function declarations that are hoisted.
"functions-and-types"
Report shadowing for both function and type declarations that are hoisted.
"never"
Never report shadowing before the outer variable is declared.
"types"
Only report shadowing for type declarations that are hoisted.
ignoreFunctionTypeParameterNameValueShadow
type: boolean
default: true
If true, ignore when a function type parameter shadows a value. Example: const T = 1; function foo<T>() {}
ignoreOnInitialization
type: boolean
default: false
Whether to ignore the variable initializers when the shadowed variable is presumably still uninitialized.
ignoreTypeValueShadow
type: boolean
default: true
If true, ignore when a type and a value have the same name. This is common in TypeScript: type Foo = ...; const Foo = ...;
How to use
To enable this rule using the config file or in the CLI, you can use:
{
"rules": {
"no-shadow": "error"
}
}import { defineConfig } from "oxlint";
export default defineConfig({
rules: {
"no-shadow": "error",
},
});oxlint --deny no-shadowVersion
This rule was added in v1.48.0.