如何在ES6类中定义类级别常量[重复]

我们如何定义类级常量并在静态方法和实例方法中访问它？

 class ExternalRequests{

      const HEADERS = { "Accept":  "application/json, text/plain", "Content-Type": "application/json", "Access-Control-Allow-Origin": "*"}


      static get(url){
        return fetch(url, {method: 'get', HEADERS})
        .catch(_ => {
          throw new Error("network error");
        })
        .then(response => {
          if (!response.ok) {
            throw new Error(response.statusText);
          }
          return response.json();
        });
      }

      static post(url, data){
        return fetch(url, {method: 'post', HEADERS, body: data})
        .catch(_ => {
          throw new Error("network error");
        })
        .then(response => {
          if (!response.ok) {
             throw new Error(response.statusText);
          }
          return response.json();
        });
      }

     static put(url, data){
        return fetch(url, {method: 'put', HEADERS, body: data})
        .catch(_ => {
          throw new Error("network error");
        })
        .then(response => {
          if (!response.ok) {
            throw new Error(response.statusText);
          }
          return response.json();
        });
      }

      static delete(){
       return fetch(url, {method: 'delete', HEADERS})
        .catch(_ => {
          throw new Error("network error");
        })
        .then(response => {
          if (!response.ok) {
            throw new Error(response.statusText);
          }
          return response.json();
        });
      }

    }

    export default ExternalRequests;

ERROR

ERROR in ./externalRequests.js
Module build failed: SyntaxError: Unexpected token (3:8)

  1 | class ExternalRequests{
  2 | 
> 3 |   const HEADERS = { "Accept":  "application/json, text/plain", "Content-Type": "application/json", "Access-Control-Allow-Origin": "*"}

将其更改为static get访问器。然后您可以访问它this.HEADERS来自其他静态方法。 （不幸的是，这是在 JS 获取类属性之前我们得到的最好的结果）

class ExternalRequests{
  static get HEADERS() {
    return { 
      "Accept":  "application/json, text/plain", 
      "Content-Type": "application/json", 
      "Access-Control-Allow-Origin": "*"
    }
  }

  static get(url){
    return fetch(url, {method: 'get', this.HEADERS})
  }
/* rest of the class ... */

如果您现在想使用类属性，您可以使用babel-transform-class-properties https://babeljs.io/docs/plugins/transform-class-properties/，这将允许您执行以下操作：

class ExternalRequests {
  static HEADERS = /* ... your headers */
  /* ...rest of the class... */