角度4-错误TypeError:无法读取未定义的属性'push' [英] Angular 4 - ERROR TypeError: Cannot read property 'push' of undefined

问题描述

这是我的组件代码.我正在使用socket.on从节点服务器获取数据，然后将其推送到Typescript数组中.其在推送功能上显示错误.实际上，列表数组目前尚未定义.

this is my component code. and i am using socket.on to get data from node server and then want to push that into a Typescript array. its showing error on push function. actually list array is undefined at this point.

import { Component } from '@angular/core';
import * as io from 'socket.io-client';
    @Component({
  selector: 'app-admin',
  templateUrl: './admin.component.html',
  styleUrls: ['./admin.component.css']
})
export class AdminComponent{

private socket: io.Socket;
private list: any[];

  constructor() { 
      this.socket = io('wss://ngrk-buzzer-app.herokuapp.com');
      this.socket.on('message', function (data) {
            console.log(data);
            this.list.push(data.from + " pressed Buzzer."); //this is where the error is 
    });
  }

  clearList(){

      this.socket.emit("clear", "yes");

  }

  addItemInList(data){


  }



}

我应该怎么做才能定义this.list?

what should i do to make this.list make defined?

推荐答案

将变量列表初始化为一个空数组，否则当您尝试推送对象时它将是未定义的

intialize your variable list to an empty array, otherwise it will be undefined when you try to push objects

private list: any[] = [];

也可以使用箭头功能.

this.socket.on('message', (data: any) => this.list.push(data.from + " 
pressed Buzzer."); 

这篇关于角度4-错误TypeError:无法读取未定义的属性'push'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！