useGuardForIn
¥Summary
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规则生效日期：
v1.9.4¥Rule available since:
v1.9.4 -
诊断类别：
lint/suspicious/useGuardForIn¥Diagnostic Category:
lint/suspicious/useGuardForIn -
此规则没有修复方案。
¥This rule doesn’t have a fix.
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此规则的默认严重级别为 warning。
¥The default severity of this rule is warning.
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来源：
¥Sources:
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与
guard-for-in相同¥Same as
guard-for-in
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¥How to configure
{ "linter": { "rules": { "suspicious": { "useGuardForIn": "error" } } }}¥Description
要求 for-in 循环包含 if 语句。
¥Require for-in loops to include an if statement.
使用 for-in 循环遍历对象时，将包含通过原型链继承的属性。此行为可能会导致 for 循环中出现意外项。
¥Looping over objects with a for-in loop will include properties inherited through the prototype chain.
This behavior can lead to unexpected items in your for loop.
对于不支持 ES2022 的代码库，可以使用 Object.prototype.hasOwnProperty.call(foo, key) 来检查属性是否被继承。
¥For codebases that do not support ES2022, Object.prototype.hasOwnProperty.call(foo, key) can be used as a check that the property is not inherited.
对于支持 ES2022 的代码库，可以使用 Object.hasOwn(foo, key) 作为更简洁、更可靠的替代方案。
¥For codebases that do support ES2022, Object.hasOwn(foo, key) can be used as a shorter and more reliable alternative.
¥Examples
¥Invalid
for (key in foo) { doSomething(key);}code-block.js:1:1 lint/suspicious/useGuardForIn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
⚠ The body of a for-in should be wrapped in an `if` statement.
> 1 │ for (key in foo) {
│ ^^^^^^^^^^^^^^^^^^
> 2 │ doSomething(key);
> 3 │ }
│ ^
4 │
ℹ Looping over the object with for-in loop will include properties that are inherited through the prototype chain, the behaviour can lead to some unexpected items in your loop.
ℹ To resolve this issue, add an if statement like `if (Object.hasOwn(foo, key)) {…}` to filter out the extraneous properties.
¥Valid
for (key in foo) { if (Object.hasOwn(foo, key)) { doSomething(key); }}for (key in foo) { if (Object.prototype.hasOwnProperty.call(foo, key)) { doSomething(key); }}for (key in foo) { if ({}.hasOwnProperty.call(foo, key)) { doSomething(key); }}¥Related links
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