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fix

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This commit is contained in:
Ilya Kantor 2017-06-14 10:35:59 +03:00
parent 1fb7296f72
commit e37d4ac498
6 changed files with 28 additions and 23 deletions
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1-js/07-object-oriented-programming/01-property-descriptors/article.md
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@ -145,9 +145,7 @@ user.name = "Alice"; // Error
Now let's add a custom `toString` to `user`.
Normally, a built-in `toString` for objects is non-enumerable, it does not show up in `for..in`. But if we add `toString` of our own, then by default it shows up in `for..in`.
...But if we don't like it, then we can set `enumerable:false`. Then it won't appear in `for..in` loop, just like the built-in one:
Normally, a built-in `toString` for objects is non-enumerable, it does not show up in `for..in`. But if we add `toString` of our own, then by default it shows up in `for..in`, like this:
```js run
let user = {
@ -159,6 +157,17 @@ let user = {
// By default, both our properties are listed:
for(let key in user) alert(key); // name, toString
```
If we don't like it, then we can set `enumerable:false`. Then it won't appear in `for..in` loop, just like the built-in one:
```js run
let user = {
name: "John",
toString() {
return this.name;
}
};
Object.defineProperty(user, "toString", {
*!*
@ -167,7 +176,7 @@ Object.defineProperty(user, "toString", {
});
*!*
// Now toString disappears:
// Now our toString disappears:
*/!*
for(let key in user) alert(key); // name
```
@ -178,11 +187,9 @@ Non-enumerable properties are also excluded from `Object.keys`:
alert(Object.keys(user)); // name
```
## Non-configurable
The non-configurable flag (`configurable:false`) is usually set for built-in objects and properties.
The non-configurable flag (`configurable:false`) is sometimes preset for built-in objects and properties.
A non-configurable property can not be deleted or altered with `defineProperty`.