javascript - 为 JSON 属性抛出 Nan 消息

Question

我开发了一个 Angular4 应用程序，它调用 nodeExpressJS 服务器来获取 JSON 数据，并将数据添加到 JSON 对象。以下是addemployeeform的onSubmit函数。

onSubmit(formValue: any) {
    console.log("Form Value = " + JSON.stringify(formValue, null, 4));
    let newEmployee: Emp;
    let last: any;
    this._employeeService.lastEmployeeID().subscribe((last: any) => last = last,
        err => console.log(err));
    newEmployee = {
        //id: employeeCount + 1,
        id: last + 1,
        name: formValue.name,
        manufacturer: formValue.manufacturer,
        type: formValue.type,
        batchno: formValue.batchno,
        expdate: formValue.expdate,
        price: formValue.price
    };
    // console.log(newEmployee.id );
    let temp = this._employeeService.addEmployee(newEmployee).subscribe(err =>
        console.log(err));
    this.router.navigate(['employees']);
}

但是它不会将 id 属性推送到 newEmployee 的 JSON。

{id: 1, name: "Paracetamol", manufacturer: "Ranbaxy", type: "Tablet", batchno …}

{id: 2, name: "Sinarest", manufacturer: "GSK", type: "Tablet", batchno: …}

{id: 3, name: "Viagra", manufacturer: "Pfizer", type: "Capsule", batchno: …} 

{name: "Aspirine", manufacturer: "Aspirine", type: "Syrup", batchno: "03/46", expdate: "03/04/2023", …}

newEmployee 是阿司匹林。

并取消注释 console.log(newEmployee.id ); 代码行

我收到 Nan 错误

Answer 1

首先，last 不应该被定义为 number 而不是 any 吗？

其次，更重要的是，lastEmployeeId 调用很可能是异步的，这意味着在下一行代码完成之前它不会完成。您需要在订阅中添加在该操作之后执行的所有代码。

this._employeeService.lastEmployeeID().subscribe(
 (last: any) => {
    last = last;
    newEmployee = {
      //id: employeeCount + 1,
      id: last + 1,
      name: formValue.name,
      manufacturer: formValue.manufacturer,
      type: formValue.type,
      batchno: formValue.batchno,
      expdate: formValue.expdate,
      price: formValue.price
  };
  // console.log(newEmployee.id );
  let temp = this._employeeService.addEmployee(newEmployee).subscribe(
    employee => {
       console.log(employee);
       this.router.navigate(['employees']);
    },
    err => console.log(err)
  );

第一个函数中的这么多代码传递给您的订阅，您可能希望将其设为自己的函数:

this._employeeService.lastEmployeeID().subscribe(
   (last: number) => this.processEmployeeId(last),
    err => console.log(err));

processEmployeeId(last: number) {
   // Your code here.
}