如何多次调用类方法内联(链调用)JavaScript es6

Question

我尝试逐行调用类的方法,第二种方法是未定义的.

如何在ES6类中实现此模式？

await new Mail().attachments(files).send()

在mail.js

export class Mail{

    constructor(){
      this.mail =  {
         *********
         ********* 
      };
    }


    attachments(files){
      *********
      ********* 
    }

    async send(){
        try{
            return await sendmail(this.mail, function(err) {
                if(err){
                    return false
                };
                return true;
            });
        }catch(e){
            throw e;
        }


    }
}

Answer 1

你需要确保attachments结束,return this以便在它之后链接方法:

const sendmail = () => new Promise(res => setTimeout(res, 1000));
class Mail {
  constructor() {
    this.mail = 'mail';
  }
  attachments(files) {
    console.log('adding attachments');
    return this;
  }
  async send() {
    console.log('sending...');
    return sendmail(this.mail);
  }
}
(async() => {
  console.log('start');
  const files = 'files';
  await new Mail().attachments(files).send()
  console.log('end');
})();

每当您想要定义要链接的方法时,请遵循相同的模式 - return this最后为了返回实例化的对象.