handler.construct()

¥Syntax

new Proxy(target, {
  construct(target, argumentsList, newTarget) {
  }
});

¥Parameters

以下参数传递给 construct() 方法。this 绑定到处理程序。

¥The following parameters are passed to the construct() method. this is bound to the handler.

target

目标对象。

argumentsList

构造函数的参数列表。

newTarget

最初调用的构造函数。

¥Return value

construct 方法必须返回一个对象。

¥The construct method must return an object.

¥Description

¥Interceptions

该陷阱可以拦截以下操作：

¥This trap can intercept these operations:

• new 运算符：new myFunction(...args)
• Reflect.construct()

或调用 [[Construct]] 内部方法 的任何其他操作。

¥Or any other operation that invokes the [[Construct]] internal method.

¥Invariants

如果违反以下不变量，则陷阱在调用时会抛出 TypeError。

¥If the following invariants are violated, the trap throws a TypeError when invoked.

• 结果必须是 Object。

¥Examples

¥Trapping the new operator

以下代码捕获 new 运算符。

¥The following code traps the new operator.

const p = new Proxy(function () {}, {
  construct(target, argumentsList, newTarget) {
    console.log(`called: ${argumentsList}`);
    return { value: argumentsList[0] * 10 };
  },
});

console.log(new p(1).value); // "called: 1"
// 10

以下代码违反了不变量。

¥The following code violates the invariant.

const p = new Proxy(function () {}, {
  construct(target, argumentsList, newTarget) {
    return 1;
  },
});

new p(); // TypeError is thrown

以下代码未正确初始化代理。代理初始化中的 target 本身必须是 new 运算符的有效构造函数。

¥The following code improperly initializes the proxy. The target in Proxy initialization must itself be a valid constructor for the new operator.

const p = new Proxy(
  {},
  {
    construct(target, argumentsList, newTarget) {
      return {};
    },
  },
);

new p(); // TypeError is thrown, "p" is not a constructor

¥See also

• Proxy
• Proxy() 构造函数
• new
• Reflect.construct()