javascript - 如何将字符串参数从 Angular UI 传递到 node.js 后端？

Question

我正在尝试将一个字符串值从 Angular UI 传递到 node.js 后端 api，然后使用传递的字符串值在 mongodb 中搜索，如下所示。

我尝试在 enteredValue 中获取输入并将其作为 params:this.enteredValue 传递给 http.get 调用并传递给 Node .js as req.params，正如您在下面看到的，如果我对“orgChange”的字符串值进行硬编码，它工作正常但不知何故传递参数不起作用并抛出错误？关于如何修复的任何指导这个？

html:

<textarea rows="6" [(ngModel)]="enteredValue"></textarea>
<hr>
<button (click)="get_change_lifecycle_data()">Search</button>

<p>{{newPost | json }}</p>

组件

import { Component, OnInit, Injectable } from '@angular/core';
import { HttpClient } from "@angular/common/http";
import { Subject } from "rxjs";
import { map } from 'rxjs/operators';

@Component({
  selector: 'app-change-input',
  templateUrl: './change-input.component.html',
  styleUrls: ['./change-input.component.css']
})


export class ChangeInputComponent  {

constructor(private http: HttpClient) {}

enteredValue : any;
newPost : any;
get_change_lifecycle_data(){
     this.http.get('http://localhost:3000/api/change_life_cycle2',{params:this.enteredValue}).subscribe(response => {
     console.log(response);
      this.newPost = response
      });
}

}

Node .js

硬编码“orgChange”的字符串值，它工作正常

app.get("/api/change_life_cycle", (req, res, next) => {
 Change_life_cycle.find({ orgChange: "51918661" }).then(documents => {
    res.status(200).json({
      message: "Posts fetched successfully!",
      posts: documents
    });
  });
});

带有 req.params 的 API

   app.get("/api/change_life_cycle2", (req, res, next) => {
    console.log(req.body)
     Change_life_cycle.find({ orgChange: req.params }).then(documents => {
        res.status(200).json({
          message: "Posts fetched successfully!",
          posts: documents
        });
      });
    });

错误:--

(node:75156) UnhandledPromiseRejectionWarning: CastError: Cast to string failed for value "{}" at path "orgChange" for model "change_life_cycle"
    at new CastError (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/error/cast.js:29:11)
    at SchemaString.cast (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/schema/string.js:553:11)
    at SchemaString.SchemaType.applySetters (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/schematype.js:948:12)
    at SchemaString.SchemaType._castForQuery (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/schematype.js:1362:15)
    at SchemaString.castForQuery (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/schema/string.js:609:15)
    at SchemaString.SchemaType.castForQueryWrapper (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/schematype.js:1331:15)
    at cast (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/cast.js:252:34)
    at model.Query.Query.cast (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/query.js:4576:12)
    at model.Query.Query._castConditions (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/query.js:1783:10)
    at model.Query.<anonymous> (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/query.js:1810:8)
    at model.Query._wrappedThunk [as _find] (/Users/username/Downloads/mongodb-03-finished/node_modules/mongoose/lib/helpers/query/wrapThunk.js:16:8)
    at process.nextTick (/Users/username/Downloads/mongodb-03-finished/node_modules/kareem/index.js:369:33)
    at process._tickCallback (internal/process/next_tick.js:61:11)
(node:75156) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:75156) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Answer 1

你能尝试使用HttpParams吗:

get_change_lifecycle_data(){
     const params = new HttpParams().set('params', this.enteredValue);
     this.http.get('http://localhost:3000/api/change_life_cycle2',{params})
     .subscribe(response => {
          console.log(response);
          this.newPost = response
      });
}

在 node 中使用 req.query 访问参数:

   app.get("/api/change_life_cycle2", (req, res, next) => {
    console.log(req.body)
     Change_life_cycle.find({ orgChange: req.query.params }).then(documents => {
        res.status(200).json({
          message: "Posts fetched successfully!",
          posts: documents
        });
      });
    });