The project describes to check a username or email address exists or not in the backend.

1.Create an angular project with the below command.

ng new angular-material-forms-username-availability

2. After successful creation of the angular app, change the file directory to project-name. “cd angular-material-forms-username-availability”

Open the project in vs code using “code .” in terminal or open with vs code. Then run the project using “ng serve” in the terminal. Open project in chrome using ***localhost:4200***

3. Open the app component in vs code and remove the content which is created by angular CLI while creating the app.

For Adding angular material using the command **ng add @angular/material**

4. Select theme, Am selecting Indigo/Pink, and click the below items as “yes”

• Set up global Angular Material typography styles? Am selecting y
• Set up browser animations for Angular Material? (Y/n) Select ‘y’.

5. Created Shared Module in the libs folder using “ng generate module shared”. And import, export material modules in “shared.module.ts”. And also add in the app.module.ts

shared.module.ts

6. Create the Signup component in the apps/component folder. And add the signup component in router and path as signup.

7. Add “ReactiveFormsModule”, and “FormsModule” in app.module.ts as below.

import { FormsModule, ReactiveFormsModule } from '@angular/forms'; @NgModule({
declarations: [
AppComponent,
SignupComponent
],
imports: [
BrowserModule,
AppRoutingModule,
BrowserAnimationsModule,
FormsModule,
ReactiveFormsModule,
SharedModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }

8. Open “signup.component.ts”, then add “formbuilder ” as a dependency in the constructor. Create a form variable above the constructor.

import { FormArray, FormBuilder, FormGroup, Validators } from ‘@angular/forms’;

public form:FormGroup;

constructor(private fb:FormBuilder) { }

ngOnInit(): void { }

9. Create formInit method to initialize the form and call the method from either constructor or ngOnInit.

constructor(private fb:FormBuilder) {
this.formInit()
}
ngOnInit(): void { }

private formInit(){
}

10. And create a form group using form builder and add controls in that same form. Form Controls like “firstName”, “secondName”, “email”, “username”, “password”, and “mobile”.

private formInit(){
this.form = this.fb.group({
firstName: [‘’,[Validators.required]],
lastName: [‘’,[Validators.required]],
username: [‘’,[Validators.required]],
email: [‘’,[Validators.required]],
password: [‘’,[Validators.required]],
});
}

11. After successfully following the above points. Add Html in signup.component.html related to form step by step.

• Add div and form tag in HTML file.

• Increase code by one form control and add validate message also.

• Add all the controls and form validation messages.

12. After successfully adding the Html code and checking the changes in the browser. Add the submit method in signup.component.ts

public submitForm(){
console.log(this.form);
console.log(this.form.getRawValue())
}

13. Test the form by giving all the forms and clicking on submit. You can able to see the values in the console.

14. And if you did not give values in the form you can able to see the error messages.

15. For checking username and email availability we need to create verifyUsernameOrEmail(fieldName) method.

public verifyUsernameOrEmail(fieldName){
const field = this.form.get(fieldName);
if(field.valid){
console.log(field.value)
}
}

16. After that add below two form value changes listeners inside ngOnInit() as mentioned below and also call the above method.

this.form
.get('username')
.valueChanges
.subscribe( (value) => {
this.verifyUsernameOrEmail('username');
});

this.form
.get('email')
.valueChanges
.subscribe( (value) => {
this.verifyUsernameOrEmail('email');
});

17. Create a user service file under the app/apis folder and add it as a dependency in signup.component.ts.

constructor(private fb:FormBuilder, private api:UserServiceService) {
this.formInit();
}

To generate a service file enter the command in the terminal as below.

ng generate service user-service

18. Add the verifyUsernameOrEmail(filter?) method in the service file and add the get endpoint for checking the availability of username or email like below.

constructor(private http:HttpClient) { }

public verifyUsernameOrEmail(filter){
let params = new HttpParams();
if(filter){
if(filter.username){
params = params.append('username', filter.username);
}
if(filter.email){
params = params.append('email', filter.email);
}
}

return this.http.get('localhost:3000/public/user/availability',{params})
}

19. Call the service method from the signup component inside of the verifyUsernameOrEmail() like below and also test the service by changing username or email.

public verifyUsernameOrEmail(fieldName){
const field = this.form.get(fieldName);
if(field.valid){
const filter = {}
filter[fieldName] = field.value;
this.api.verifyUsernameOrEmail(filter).subscribe((res: any )=> {
console.log(res.availability)
},
error=>{
console.log(error)
})
}
}

20. After checking the console logs add the logic to display custom validation errors in the UI as below.

const filter = {}
filter[fieldName] = field.value;
this.api.verifyUsernameOrEmail(filter).subscribe((res: any )=> {
if(res?.availability){
const message = fieldName === 'email' ? 'Email already Exists.' : 'Username already Exists.'
fieldName === 'email' ?
field.setErrors({ inValidEmail: true, message}) :
field.setErrors({ inValidUserName: true, message})
}
else{
field.setErrors(null);
fieldName === 'email' ?
field.setValidators([Validators.required,Validators.email]) :
field.setValidators([Validators.required, Validators.minLength(4),Validators.maxLength(20)])
}

21. As per the above diagram if the username is there am setting Errors as Invalid Username is true else am setting it as null, adding existing validators to the field, and also using similar logic for email.

22. To display error messages in Html you need to add the below lines of code to the existing code.

To test the output by running the project, see the output by opening URL(localhost:4200/signup) in browser parallelly run backend also by using npm run dev command.

Output Screens:

Screen #1(All Errors)

Screen #2 (Username & Email already exists)

Screen #3(If username and email id not exists)

Source Code

Frontend
GitHub: mryenagandula/angular-material-forms-username-availability

Backend
GitHub: mryenagandula/Letstalk-Backend

Live Backend URI: letstalk-be.herokuapp.com

Stack blitz Project Preview:

stackblitz.com/edit/github-angular-material..

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