如何在Angular中处理空值 [英] How to handle null values in Angular

问题描述

我正在将数据发送到Angular，但记录的值(截止日期)之一为空.我如何在Angular中处理此问题，以便如果value为null，则将其更改为-

I am sending data to Angular but one of the value (closed date) for a record is null. How can I handle this in Angular so that if value is null , it changed to --

  getDetails() {
    this.myService.getFlowerDetails(this.flowerId, this.flowerName).subscribe(
      res => {
        this.flower = res;
        if(this.flower !== undefined){
          this.flowerName = this.flower.flowerName;
          this.flowerId = this.flower.flowerId.toString();
          this.flowerCategory = this.flower.flowerCategory;
          this.recordCreateDate = this.flower.recordCreateDate.toString();
          this.recordClosedDate = this.flower.recordClosedDate.toString(); // this is null in the backend
        }
        else{
          this.flowerName = "--";
          this.flowerId = "--";
          this.flowerCategory = "--";
          this.recordCreateDate = "--";
          this.recordClosedDate = "--";
        }
      }, er => {
    this.throwError = er;
});

我收到以下错误.这不是整个堆栈跟踪(不确定是否需要)

I get the following error. This is not the entire stack trace (not sure if its needed)

TypeError
​
columnNumber: 17
​
fileName: "http://localhost:4200/main.bundle.js"
​
lineNumber: 1738
​
message: "_this.flower.recordClosedDate is null"

推荐答案

在 this.flower.recordClosedDate 的情况下， || 运算符可用于设置默认值.code>是虚假的( undefined ， null ，空字符串，零):

The || operator can be used to set a default value, in cases where this.flower.recordClosedDate is falsy (undefined, null, empty string, zero):

this.recordClosedDate = (this.flower.recordClosedDate || "--").toString();

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