handler.isExtensible()
The handler.isExtensible()
method is a trap for
Object.isExtensible()
.
Syntax
const p = new Proxy(target, {
isExtensible: function(target) {
}
});
Parameters
The following parameter is passed to the isExtensible()
method.
this
is bound to the handler.
target
- The target object.
Return value
The isExtensible()
method must return a boolean value.
Description
The handler.isExtensible()
method is a trap for
Object.isExtensible()
.
Interceptions
This trap can intercept these operations:
Invariants
If the following invariants are violated, the proxy will throw a
TypeError
:
Object.isExtensible(proxy)
must return the same value asObject.isExtensible(target)
.
Examples
Trapping of isExtensible
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
Specifications
Browser compatibility
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