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@babel/plugin-transform-class-properties

信息

此插件包含在 @babel/preset-env 中，在 ES2022 中

¥This plugin is included in @babel/preset-env, in ES2022

示例​

¥Example

下面是一个具有四个类属性的类，它们将被转换。

¥Below is a class with four class properties which will be transformed.

JavaScript
class Bork {
  //Property initializer syntax
  instanceProperty = "bork";
  boundFunction = () => {
    return this.instanceProperty;
  };

  //Static class properties
  static staticProperty = "babelIsCool";
  static staticFunction = function() {
    return Bork.staticProperty;
  };
}

let myBork = new Bork();

//Property initializers are not on the prototype.
console.log(myBork.__proto__.boundFunction); // > undefined

//Bound functions are bound to the class instance.
console.log(myBork.boundFunction.call(undefined)); // > "bork"

//Static function exists on the class.
console.log(Bork.staticFunction()); // > "babelIsCool"

安装​

¥Installation

npm install --save-dev @babel/plugin-transform-class-properties

用法​

¥Usage

¥With a configuration file (Recommended)

没有选项：

¥Without options:

babel.config.json
{
  "plugins": ["@babel/plugin-transform-class-properties"]
}

有选项：

¥With options:

babel.config.json
{
  "plugins": [["@babel/plugin-transform-class-properties", { "loose": true }]]
}

通过 CLI​

¥Via CLI

Shell
babel --plugins @babel/plugin-transform-class-properties script.js

通过 Node API​

¥Via Node API

JavaScript
require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-transform-class-properties"],
});

选项​

¥Options

loose​

boolean，默认为 false。

¥boolean, defaults to false.

当 true 时，类属性被编译为使用赋值表达式而不是 Object.defineProperty。

¥When true, class properties are compiled to use an assignment expression instead of Object.defineProperty.

提醒

考虑迁移到顶层 setPublicClassFields 假设

¥Consider migrating to the top level setPublicClassFields assumption

babel.config.json
{
  "assumptions": {
    "setPublicClassFields": true
  }
}

有关使用任一后果的说明，请参阅 定义与赋值（TL；DR in Part 5）

¥For an explanation of the consequences of using either, see Definition vs. Assignment (TL;DR in Part 5)

示例​

¥Example

JavaScript
class Bork {
  static a = "foo";
  static b;

  x = "bar";
  y;
}

当 setPublicClassFields 为 false 时，上面的代码将编译为以下代码，使用 Object.defineProperty：

¥When setPublicClassFields is false, the above code will compile to the following, using Object.defineProperty:

JavaScript
var Bork = function Bork() {
  babelHelpers.classCallCheck(this, Bork);
  Object.defineProperty(this, "x", {
    configurable: true,
    enumerable: true,
    writable: true,
    value: "bar",
  });
  Object.defineProperty(this, "y", {
    configurable: true,
    enumerable: true,
    writable: true,
    value: void 0,
  });
};

Object.defineProperty(Bork, "a", {
  configurable: true,
  enumerable: true,
  writable: true,
  value: "foo",
});
Object.defineProperty(Bork, "b", {
  configurable: true,
  enumerable: true,
  writable: true,
  value: void 0,
});

当 setPublicClassFields 设置为 true 时，它将使用赋值表达式进行编译：

¥When setPublicClassFields is set to true, it will compile using assignment expressions:

JavaScript
var Bork = function Bork() {
  babelHelpers.classCallCheck(this, Bork);
  this.x = "bar";
  this.y = void 0;
};

Bork.a = "foo";
Bork.b = void 0;
提示

你可以阅读有关配置插件选项 此处 的更多信息

¥You can read more about configuring plugin options here

参考​

¥References