无法读取未定义的属性"push"? [英] Cannot read property 'push' of undefined?

问题描述

我有以下简单代码:

  export class Years {

      private years: number[];
      private currentYear: number;

      constructor() {
        this.currentYear = new Date().getFullYear();
        this.years.push(this.currentYear + 1);
        for (let i = this.currentYear; i < this.currentYear - 5; i--) {
          this.years.push(i);
        }
      }
}

它给我一个错误:Cannot read property 'push' of undefined??为什么我有正确的数据类型作为数组?

It gives me an error: Cannot read property 'push' of undefined?? Why if I have correct data type as array?

推荐答案

您必须将年份初始化为空数组，否则为null

You have to initialize years to empty array, otherwise it is null

 private years: number[] = [];

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