class中的static

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参考资料

类（class）通过 static 关键字定义静态方法。不能在类的实例上调用静态方法，而应该通过类本身调用。这些通常是实用程序方法，例如创建或克隆对象的功能。

class ClassWithStaticMethod {
  static staticMethod() {
    return 'static method has been called.';
  }
}

console.log(ClassWithStaticMethod.staticMethod());
// expected output: "static method has been called."

let a = new ClassWithStaticMethod();

a.staticMethod() // 报错

在一个静态方法中调用同一个类中的其他静态方法，可以使用this关键字。

class StaticMethodCall {
    static staticMethod() {
        return 'Static method has been called';
    }
    static anotherStaticMethod() {
        return this.staticMethod() + ' from another static method';
    }
}
StaticMethodCall.staticMethod();
// 'Static method has been called'

StaticMethodCall.anotherStaticMethod();
// 'Static method has been called from another static method'

非静态方法中，不能直接使用 this 关键字来访问静态方法。而是要用类名来调用：CLASSNAME.STATIC_METHOD_NAME()，或者用构造函数的属性来调用该方法： this.constructor.STATIC_METHOD_NAME()

class StaticMethodCall {
    constructor() {
        console.log(StaticMethodCall.staticMethod());
        // 'static method has been called.'
        console.log(this.constructor.staticMethod());
        // 'static method has been called.'
    }
    static staticMethod() {
        return 'static method has been called.';
    }
}