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Code Issues Releases Wiki Activity

docs(Symbol): edit Symbol.unscopables

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Ruan YiFeng 2017-01-25 09:24:20 +08:00 committed by GitHub
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commit dcb12a1be9
1 changed files with 7 additions and 5 deletions
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docs/symbol.md
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@ -807,18 +807,19 @@ Array.prototype[Symbol.unscopables]
// entries: true,
// fill: true,
// find: true,
// findIndex: true,
//   findIndex: true,
// includes: true,
// keys: true
// }
Object.keys(Array.prototype[Symbol.unscopables])
// ['copyWithin', 'entries', 'fill', 'find', 'findIndex', 'keys']
// ['copyWithin', 'entries', 'fill', 'find', 'findIndex', 'includes', 'keys']
```
上面代码说明，数组有6个属性，会被with命令排除。
上面代码说明，数组有7个属性，会被`with`命令排除。
```javascript
// 没有unscopables时
// 没有 unscopables 时
class MyClass {
foo() { return 1; }
}
@ -829,7 +830,7 @@ with (MyClass.prototype) {
foo(); // 1
}
// 有unscopables时
// 有 unscopables 时
class MyClass {
foo() { return 1; }
get [Symbol.unscopables]() {
@ -844,3 +845,4 @@ with (MyClass.prototype) {
}
```
上面代码通过指定`Symbol.unscopables`属性，使得`with`语法块不会在当前作用域寻找`foo`属性，即`foo`将指向外层作用域的变量。