handler.isExtensible()
method is a trap for
Object.isExtensible()
.
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const p = new Proxy(target, {
isExtensible: function(target) {
}
});
The following parameter is passed to the
isExtensible()
方法。
this
is bound to the handler.
target
The target object.
isExtensible()
method must return a boolean value.
handler.isExtensible()
method is a trap for
Object.isExtensible()
.
This trap can intercept these operations:
If the following invariants are violated, the proxy will throw a
TypeError
:
Object.isExtensible(
proxy
)
must return the same value as
Object.isExtensible(
target
)
.
The following code traps
Object.isExtensible()
.
const p = new Proxy({}, {
isExtensible: function(target) {
console.log('called');
return true;
}
});
console.log(Object.isExtensible(p)); // "called"
// true
The following code violates the invariant.
const p = new Proxy({}, {
isExtensible: function(target) {
return false;
}
});
Object.isExtensible(p); // TypeError is thrown
| 规范 |
|---|
|
ECMAScript (ECMA-262)
The definition of '[[IsExtensible]]' in that specification. |
| Desktop | Mobile | Server | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
isExtensible
|
Chrome 49 | Edge 12 | Firefox 31 | IE No | Opera 36 | Safari 10 | WebView Android 49 | Chrome Android 49 | Firefox Android 31 | Opera Android 36 | Safari iOS 10 | Samsung Internet Android 5.0 | nodejs 6.0.0 |
完整支持
不支持