Angular中数组已赋值仍提示未初始化错误如何解决？

TypeScript 是静态类型语言，要求类的所有属性必须先在类的作用域内显式声明，才能通过 this 访问对应属性。你只是在 ngOnInit 生命周期方法中给 this.sales 赋值，相当于动态给类实例添加属性，并没有提前告知 TypeScript 该类存在 sales 属性，因此类型检查阶段就会抛出该错误，和你有没有赋值没有关系。

在 AppComponent 类的属性声明区域提前声明 sales 属性即可，推荐先定义数组项的类型约束，写法如下：

import { Component } from '@angular/core';

// 先定义sales数组每一项的类型
interface SalesItem {
  brand: string;
  lastYearSale: string;
  thisYearSale: string;
  lastYearProfit: string;
  thisYearProfit: string;
}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'excel';
  // 显式声明sales属性，指定类型并初始化空数组
  sales: SalesItem[] = [];

  ngOnInit() {
    this.sales = [
      { brand: 'Apple', lastYearSale: '51%', thisYearSale: '40%', lastYearProfit: '$54,406.00', thisYearProfit: '$43,342' },
      { brand: 'Samsung', lastYearSale: '83%', thisYearSale: '96%', lastYearProfit: '$423,132', thisYearProfit: '$312,122' },
      { brand: 'Microsoft', lastYearSale: '38%', thisYearSale: '5%', lastYearProfit: '$12,321', thisYearProfit: '$8,500' },
      { brand: 'Philips', lastYearSale: '49%', thisYearSale: '22%', lastYearProfit: '$745,232', thisYearProfit: '$650,323,' },
      { brand: 'Song', lastYearSale: '17%', thisYearSale: '79%', lastYearProfit: '$643,242', thisYearProfit: '500,332' },
      { brand: 'LG', lastYearSale: '52%', thisYearSale: ' 65%', lastYearProfit: '$421,132', thisYearProfit: '$150,005' },
      { brand: 'Sharp', lastYearSale: '82%', thisYearSale: '12%', lastYearProfit: '$131,211', thisYearProfit: '$100,214' },
      { brand: 'Panasonic', lastYearSale: '44%', thisYearSale: '45%', lastYearProfit: '$66,442', thisYearProfit: '$53,322' },
      { brand: 'HTC', lastYearSale: '90%', thisYearSale: '56%', lastYearProfit: '$765,442', thisYearProfit: '$296,232' },
      { brand: 'Toshiba', lastYearSale: '75%', thisYearSale: '54%', lastYearProfit: '$21,212', thisYearProfit: '$12,533' }
    ];
  }
}

如果暂时不需要严格的类型约束，也可以简化声明为 sales: any[] = []，不推荐长期使用该写法。

内容的提问来源于stack exchange，提问作者Niall