eslint/guard-for-in Style
What it does
Require for-in loops to include an if statement.
Why is this bad?
Looping over objects with a for in loop will include properties that are inherited through the prototype chain. Using a for in loop without filtering the results in the loop can lead to unexpected items in your for loop which can then lead to unexpected behaviour.
Examples
Examples of incorrect code for this rule:
javascript
for (key in foo) {
doSomething(key);
}Examples of correct code for this rule:
javascript
for (key in foo) {
if (Object.hasOwn(foo, key)) {
doSomething(key);
}
}javascript
for (key in foo) {
if (Object.prototype.hasOwnProperty.call(foo, key)) {
doSomething(key);
}
}javascript
for (key in foo) {
if ({}.hasOwnProperty.call(foo, key)) {
doSomething(key);
}
}How to use
To enable this rule using the config file or in the CLI, you can use:
json
{
"rules": {
"guard-for-in": "error"
}
}ts
import { defineConfig } from "oxlint";
export default defineConfig({
rules: {
"guard-for-in": "error",
},
});bash
oxlint --deny guard-for-inVersion
This rule was added in v0.2.14.