如何检查电子邮件是否存在于 MySQL 数据库中

Question

我使用 Ionic 框架创建了一个注册表单，但我不知道如何检查我输入的电子邮件是否存在于数据库中，我创建了两个文件，一个 page1.page.html 文件和一个 page1.page .ts 文件。我需要一些帮助。

page1.page.html

 <ion-header >  </ion-header>
 <div class="margin">
    <form  [formGroup]="LoginForm" (ngValider)="Valide()">
      <ion-list>
     

       <ion-item>
         <ion-label> Email</ion-label>
         <ion-input class-is-invalid="registrationform.controls.email.touched && registrationform.controls.email.invalid" formControlName="email" type="email" > </ion-input>
       </ion-item>
      <div class="error-messages" >
        <ng-container *ngFor="let error of error_messages.email">
          <div classe="error-message" *ngIf="LoginForm.get('email').hasError(error.type) && (LoginForm.get('email').dirty || LoginForm.get('email').touched)">
             {{error.message}}
          </div>
        </ng-container>
      </div>
      </ion-list>
         <br><br>
         <ion-button [disabled]="!LoginForm.valid" type="valider" color="danger"  (click)="valider()"> Valider </ion-button>
       
    </form>
  </div>

page1.page.ts

 import { Component , OnInit } from '@angular/core';
    import { FormBuilder , FormControl , FormGroup, Validators } from '@angular/forms';
    import { NavController } from '@ionic/angular';
    @Component({
      selector: 'app-page1',
      templateUrl: './page1.page.html',
      styleUrls: ['./page1.page.scss'],
    })
    export class Page1Page implements OnInit{
    LoginForm: FormGroup;
    l;
    m;
     error_messages = {
      
        email: [
          {type:'required', message: 'un email est obligatoire'},
          {type: 'minLength', message: 'une adresse email doit etre plus long ou égal à 6 caractères'},
          {type: 'maxLength', message: 'une adresse email doit etre inférieur ou égal à 50 caractères'},
          {type: 'pattern', message: 'veuillez entrer un email valide'},
         
        ]
      };
      constructor(public FormBuilder: FormBuilder , private NavCtrl :NavController) { }
      ngOnInit(){
      this.LoginForm = this.FormBuilder.group({
       
    
        email: ['', [Validators.required, Validators.minLength(6) , Validators.maxLength(50) , Validators.pattern('^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$')]],
       
      });
    }
    valider(){
      console.log("email",this.LoginForm.get('email').value);
      console.log(this.LoginForm.value);
    }
     
    }

我在后端使用节点 Nodejs，这是我的服务器端代码。

server.js

   const express = require('express') 
const http=require('http')
var app = express();
path = require('path');

var mysql  = require('mysql');
  var con = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "",
    database:"projet_pfe"
  });
  
  con.connect(function(err) {
    if (err) throw err;
    console.log("Connected OK!"); 
  });

  let server = http.createServer();
  server.listen(7000);