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How can I validate an angular form

I have this inscription form. I tried to validate it but in vain. inputs are saved in my database despite they are empty I want to have these validations:
All inputs are required
email address should be valid
name should be composer by only letters
Password should have minimum 8 characters, at least 1 uppercase
letter, 1 lowercase letter and 1 number
I want to have a message under evey invalid input.(in <div id="na"></div> for example).How can I do this please?
HTML file
<h2 class="text-center">Inscription</h2>
<div class="row">
<div class="col-md-3">
</div>
<div class="col-md-6 col-md-offset-3">
<div class="jumbotron">
<form [formGroup]="angForm" (ngSubmit)="postdata(angForm)" autocomplete="off">
<div class="form-group mb-3">
<label for="name">Nom</label>
<input type="text" name="name" formControlName="name" autocomplete="off" id="name"
class="form-control input-sm" placeholder="Nom">
</div>
<div id="na"></div>
<div class="form-group mb-3">
<label for="email">Email</label>
<input type="email" name="email" formControlName="email" autocomplete="off" id="email"
class="form-control input-sm" placeholder="Email">
</div>
<div id="mail"></div>
<div class="form-group mb-3">
<label for="Password">Mot de passe</label>
<input type="password" name="Password" formControlName="password" autocomplete="off"
id="password" class="form-control input-sm" placeholder="Mot de passe">
</div>
<div id="pwd"></div>
<button type="sumit" class="btn btn-success">Enregistrer</button>
</form>
</div>
</div>
<div class="col-md-3">
</div>
</div>
Type script file
import { Component, OnInit } from '#angular/core';
import { FormGroup, FormControl, FormBuilder, Validators, NgForm } from '#angular/forms';
import { first } from 'rxjs/operators';
import { Router } from '#angular/router';
import { ApiService } from '../api.service';
#Component({
selector: 'app-inscription',
templateUrl: './inscription.component.html',
styleUrls: ['./inscription.component.css']
})
export class InscriptionComponent implements OnInit {
angForm: FormGroup;
constructor(private fb: FormBuilder,private dataService: ApiService,private router:Router) {
this.angForm = this.fb.group({
email: [],
password: [],
name: [],
mobile: []
});
}
ngOnInit() {
}
postdata(angForm1:any){this.dataService.userregistration(angForm1.value.name,angForm1.value.email,angForm1.value.password)
.pipe(first())
.subscribe(
data => {
this.router.navigate(['login']);
},
error => {
});
}
get email() { return this.angForm.get('email'); }
get password() { return this.angForm.get('password'); }
get name() { return this.angForm.get('name'); }
}
thanks in advance

this.angForm = this.fb.group({
email: ['', Validators.required, Validators.email],
password: ['', Validators.required, Validators.minLength(8), Validators.pattern("(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,}")],
name: ['', Validators.required, Validators.pattern('^[a-zA-Z ]*$')],
mobile: [null, Validators.required, Validators.minLength(10), Validators.maxLength(10)]
});
This is the syntax for Validations.
In HTML, before closing of form-group div write
<span class="text-danger"
*ngIf="(angForm.name.touched || submitted) &&
angForm.name.errors?.required">
Name is required
</span>
<span class="text-danger"
*ngIf="((angForm.password.touched || submitted) &&
angForm.password.errors?.required )|| (angForm.invalid && submitted)">
Must contain at least one number and one uppercase and lowercase letter, and at least 8 or more characters </span>
same applies for email, mobile error msg in HTML.
Please refer for reactive form validation.
https://www.freecodecamp.org/news/how-to-validate-angular-reactive-forms/

response to Rothitha
If you don't want to use the "auxiliar variable" submitted you can use in submit.
submit(form:FormGroup)
{
if (form.invalid)
form.markallAsTouched()
else
{
..doSomething..
}
}
If we can better mannagement about errors (remove this ugly *ngIf="angForm.get('password').touched && angForm.get('password').touched" we can use a tecnica similar bootstrap mannage the error
We use a .css like
.invalid-feedback
{
display:none
}
.ng-invalid.ng-touched ~ .invalid-feedback
{
display: block;
}
And an html like
<!--enclosed all under a div-->
<div>
<!--a label-->
<label for="email">Email</label>
<!--a input-->
<input id="email" formControlName="email">
<!--a div class="invalid-feedback-->
<div class="invalid-feedback">
<!--if there're several validators use *ngIf-->
<div *ngIf="angForm.controls.email.errors?.required">Email is required</div>
<div *ngIf="angForm.controls.email.errors?.email">it's not a valid email</div>
</div>
</div>
See stackblitz

How do I add specific validation to reactive forms on angular

I'm trying to render a div based on specific errors, my form works but is buggy and is trowing a type error, "undefined is not an object" , and i don't understand why; can someone help me understand what I'm missing? I've tried simplifying my code by using just the .errors propery, that takes the errors away but its not specific enough to so that it knows what error to render depending on the state of the form, any insight would be super helpful :)
HTML
<form [formGroup]="form">
<div class="spacer">
<label for="oldPassword">Old Password</label><br /><input
type="text"
class="form-control"
id="oldPassword"
formControlName="oldPassword"
/>
<div class="alert alert-danger" *ngIf="form.get('oldPassword').errors.passwordValidator">Duplicate Password</div>
<div class="alert alert-danger" *ngIf="form.get('oldPassword').touched && form.get('oldPassword').errors.required">Old Password is Required</div>
<div *ngIf="forms.get('oldPassword').pending">Loading...</div>
</div>
<div class="spacer">
<label for="newPassword">New Password</label><br /><input
type="text"
class="form-control"
id="newPassword"
formControlName="newPassword"
/>
<div *ngIf="form.get('newPassword').touched && newPassword.invalid" class="alert alert-danger">New Password is Required</div>
</div>
<div class="spacer">
<label for="confirmPassword">Confirm Password</label><br /><input
type="text"
class="form-control"
id="confirmPassword"
formControlName="confirmPassword"
/>
<div *ngIf="confirmPassword.touched && confirmPassword.invalid" class="alert alert-danger">Confirm Password is Required</div>
</div>
<button class="btn btn-primary" (click)="onClick()">Submit!</button>
</form>
{{ oldPassword | json}}
TS:
import { Component } from '#angular/core';
import { FormBuilder, Validators, FormGroup, FormControl,} from '#angular/forms'
import { CustomValidators } from '../passwordValidator';
#Component({
selector: 'app-form',
templateUrl: './form.component.html',
styleUrls: ['./form.component.css']
})
export class FormComponent {
form = new FormGroup({
oldPassword: new FormControl('',Validators.required, CustomValidators.passwordValidator),
newPassword: new FormControl('',Validators.required),
confirmPassword: new FormControl('',Validators.required)
})
onClick() {
console.log(this.form.get('oldPassword').errors)
}
}
//CustomValidators.passwordValidator
CUSTOM VALIDATOR.TS
import { AbstractControl, ValidationErrors, } from '#angular/forms';
export class CustomValidators {
static passwordValidator(control: AbstractControl): Promise<ValidationErrors | null> {
return new Promise((resolve, reject) => {
setTimeout(() => {
if (control.value === "123") {
resolve({ passwordValidator: true })
}
resolve(null)
}, 2000);
});
}
}
Here is the error

You have some issues...
<div *ngIf="forms.get('oldPassword').pending">Loading...</div>, remove the s from forms
<div *ngIf="confirmPassword.touched && confirmPassword.invalid" is invalid
*ngIf="form.get('newPassword').touched && newPassword.invalid" is invalid
Your custom async validator should be placed as the third argument
Those undefined issues stem from errors being null
Suggestion: Use FormBuilder instead of calling new FormControl(), but I'll keep my sample with your current code. Also usually we use ngSubmit instead of click event in forms.
So first place the async validator in correct place:
oldPassword: new FormControl(
"",
[Validators.required],
[CustomValidators.passwordValidator]
),
The rest of the errors is related to that errors being null in template if there are no errors... where you are calling such as...
*ngIf="form.get('oldPassword').errors.passwordValidator"
You could solve this by adding the safe navigation operator:
*ngIf="form.get('oldPassword').errors?.passwordValidator"
That will work, but I use the following way, which is in my opinion nicer and more intuitive:
*ngIf="form.hasError('passwordValidator', 'oldPassword')"
So here's a stripped down, shortened version of your code:
<form [formGroup]="form" (ngSubmit)="onClick()">
<label for="oldPassword">Old Password</label><br />
<input formControlName="oldPassword" />
<div *ngIf="form.hasError('passwordValidator', 'oldPassword')">
Duplicate Password
</div>
<div *ngIf="form.get('oldPassword').touched && form.hasError('required', 'oldPassword')">
Old Password is Required
</div>
<div *ngIf="form.get('oldPassword').pending">Loading...</div>
<button type="submit" [disabled]="!form.valid">Submit!</button>
</form>
STACKBLITZ

Cannot read property of custom Validator and required - Angular

I'm try to make custom Validators that give user message when he/she leave a space on text but i received this error.
1-Cannot read property 'removeSpaceFromUserName' of undefined
2-Cannot read property 'required' of null
at Object.eval [as updateDirectives]
Here's the html of the component
<form [formGroup]='form'>
<div class="form-group">
<label for="username">Username</label>
<input
formControlName='username'
id="username"
type="text"
class="form-control">
<div *ngIf="username.touched && username.touched" class="alert alert-danger">
<div *ngIf="username.errors.required"> You need to enter user name</div>
<div *ngIf="username.errors.minlength"> Min Length is
{{ username.errors.minLength.requiredLength}}
</div>
<div *ngIf="UserNameValiditors.removeSpaceFromUserName">
removeSpaceFromUserName </div>
</div>
</div>
<div class="form-group">
<label for="password">Password</label>
<input
formControlName='password'
id="password"
type="text"
class="form-control">
</div>
<button class="btn btn-primary" type="submit">Sign Up</button>
</form>
Here's the custom validator class
import { AbstractControl, ValidationErrors } from "#angular/forms";
export class UserNameValiditors {
static removeSpaceFromUserName(control: AbstractControl): ValidationErrors | null {
if ((control.value as string).indexOf(' ') >= 0) {
return {
removeSpaceFromUserName: true
};
}
else {
return null;
}
}
}
import { Component } from '#angular/core';
import { FormControl , FormGroup , Validators } from "#angular/forms";
import { UserNameValiditors } from './UserNameValditors';
#Component({
selector: 'signup-form',
templateUrl: './signup-form.component.html',
styleUrls: ['./signup-form.component.css']
})
export class SignupFormComponent {
form= new FormGroup(
{
username : new FormControl('',
[
Validators.required,
Validators.minLength(3) ,
UserNameValiditors.removeSpaceFromUserName
]) ,
password : new FormControl('',Validators.required)
});
get username()
{
return this.form.get('username');
}
}

You can try with this solution.
I have create a demo on Stackblitz
app.component.ts
myForms: FormGroup;
constructor(fb: FormBuilder) {
this.myForms = fb.group({
username: [null, Validators.compose([
Validators.required, Validators.minLength(3), usernameValidator])],
password: [null, [
Validators.required]]
});
}
app.component.html
<form [formGroup]="myForms">
<label>User Name :
<input type="text" formControlName="username">
</label><br>
<div class="errors" *ngIf="myForms.get('username').invalid && (myForms.get('username').touched || myForms.get('username').dirty)">
<div *ngIf="myForms.get('username').hasError('required')">
username is required
</div>
<div *ngIf="myForms.get('username').errors.minlength">
username must be at least 3 characters
</div>
<div class="error-text" *ngIf="myForms.get('username').hasError('removeSpaceFromUserName')">
removeSpaceFromUserName
</div>
</div>
<div class="form-group">
<label for="password">Password</label>
<input
formControlName='password'
id="password"
type="text"
class="form-control">
</div>
<button class="btn btn-primary" type="submit">Sign Up</button>
</form>

Use hasError() to check if certain error is present on the form.
html code
<div *ngIf="username.hasError('required')"> You need to enter user name</div>
<div *ngIf="username.hasError('minlength')"> Min Length is {{ username.hasError('minLength')}}
</div>f
<div *ngIf="username.hasError('removeSpaceFromUserName')">
removeSpaceFromUserName </div>
</div>
Your working code is here

Angular 4 Reactive Forms FormControl errors is null

If I tab through the text inputs without entering anything, the error msg divs display indicating that the required validator has fired correctly. However, if I type anything into one of the fields, the console immediately throws this error:
Cannot read property 'required' of null
Here is my component:
import { PasswordValidators } from './../validators/password.validators';
import { Component, OnInit } from '#angular/core';
import { FormBuilder, Validators, FormGroup, FormControl } from '#angular/forms';
#Component({
selector: 'app-changepassword-form',
templateUrl: './changepassword-form.component.html',
styleUrls: ['./changepassword-form.component.css']
})
export class ChangepasswordFormComponent {
form;
constructor(fb: FormBuilder) {
this.form = fb.group({
newPassword: ['', Validators.required],
confirmPassword: ['', Validators.required]
})
}
get newPassword() {
return this.form.get('newPassword');
}
get confirmPassword() {
return this.form.get('confirmPassword');
}
}
and HTML:
<form [formGroup]="form">
<div class="form-group">
<label for="newPassword">New Password</label>
<input formControlName="newPassword" id="newPassword" type="text" class="form-control">
<div class="alert alert-danger" *ngIf="newPassword.touched && newPassword.errors.required">
Required
</div>
</div>
<div class="form-group">
<label for="confirmPassword">Confirm Password</label>
<input formControlName="confirmPassword" id="confirmPassword" type="text" class="form-control">
<div class="alert alert-danger" *ngIf="confirmPassword.touched && confirmPassword.errors.required">
Required
</div>
</div>
<p><button class="btn btn-primary">Submit</button></p>
</form>

That error is coming from this:
*ngIf="newPassword.touched && newPassword.errors.required"
When you put in a value, there is no longer an errors collection so checking newPassword.errors.required generates that Cannot read property 'required' of null error.
Try something like this instead:
*ngIf="newPassword.touched && newPassword.errors?.required"
As an example, mine looks like this:
<div class="col-md-8">
<input class="form-control"
id="productNameId"
type="text"
placeholder="Name (required)"
required
minlength="3"
[(ngModel)] = product.productName
name="productName"
#productNameVar="ngModel" />
<span class="help-block" *ngIf="(productNameVar.touched ||
productNameVar.dirty || product.id !== 0) &&
productNameVar.errors">
<span *ngIf="productNameVar.errors.required">
Product name is required.
</span>
<span *ngIf="productNameVar.errors.minlength">
Product name must be at least three characters.
</span>
</span>
</div>

You can also use the following syntax and it will work without the need to have a value first:
form.get('newPassword').hasError('required')
This will check for 'required' in the errors.
This will work as well and it's more concise :
form.hasError('required','newPassword')
If you are compiling with AOT option, according to this article, you should privilege hasError() syntax:
Don’t use control.errors?.someError, use control.hasError(‘someError’)

How to use $asyncValidators with angularjs and set a warning message in the HTML

This is my first bigger form with validations and etc.
I've created a Registration form and I'm using ng-messages for validation. The problem is that I need to validate the username, does it already exist in the JSON server that we are using or it's available. Of course, if it's taken the warning pops out in the HTML where the username input is, if it's available the submit button is no more disabled (because the form will be $valid) and the user can register. I want to use angular-sanitize because I found this (I don't know if they are related):
ngModel.$asyncValidators.uniqueUsername = function(modelValue, viewValue) {
var value = modelValue || viewValue;
// Lookup user by username
return $http.get('/api/users/' + value).
then(function resolved() {
//username exists, this means validation fails
return $q.reject('exists');
}, function rejected() {
//username does not exist, therefore this validation passes
return true;
});
};
Here is the code I use now (reg form, controller and service):
// Controller:
export default class registerPageController {
constructor(userService, authenticationService, $location) {
this.register = "Register";
this.userService = userService;
this.$location = $location;
this.authenticationService = authenticationService;
this.hasLoggedIn = false;
}
onSubmit(user) {
let self = this;
let {
name,
age,
email,
username,
password
} = user;
self.userService.register(name, age, email, username, password).then((res) => {
self.userService.login(username, password).then(function (response) {
let data = response.data;
if (data.length) {
let user = data[0];
self.hasLoggedIn = true;
self.authenticationService.setCredentials(username, password);
self.$location.path('/');
}
});
})
.catch(err => {
// WHAT TO PUT HERE AFTER THE USERNAME EXIST VALIDATION ?
})
}
}
// Service:
export class UserService {
constructor($http) {
this.$http = $http;
}
login(username, password) {
return this.$http({
method: 'GET',
url: 'http://localhost:3000/users',
params: {
username: username,
password: password
}
});
}
register(name, age, email, username, password) {
return this.$http({
method: 'POST',
url: 'http://localhost:3000/users',
data: {
name: name,
age: age,
email: email,
username: username,
password: password
}
});
}
// SHOULD I PUT HERE THE USERNAME EXIST VALIDATION LOGIC ?
}
<div class="container main-content">
<form class="registrationForm" name="registerForm" ng-submit="register.onSubmit(register.user)" novalidate="novalidate">
<!-- Enter Name -->
<div class="form-group">
<label for="name" class="control-label"><span id="reqInfo">*</span> Name</label>
<input type="text" name="name" class="form-control" ng-model="register.user.name" ng-pattern="/[a-zA-Zа-яА-Я]+/" id="name"
required="" placeholder="Example: Petar Petrov">
<div ng-messages="registerForm.name.$error" ng-show="registerForm.name.$touched" style="color:maroon" role="alert">
<div ng-message="required">Your name is required</div>
</div>
</div>
<!-- User Age-->
<div class="form-group">
<label for="age" class="control-label"><span id="reqInfo">*</span> Age</label>
<input type="number" name="age" class="form-control" ng-model="register.user.age" ng-min="18" min="18" id="age" required=""
placeholder="Enter your age">
<div ng-messages="registerForm.age.$error" ng-show="registerForm.age.$touched" style="color:maroon" role="alert">
<div ng-message="min">You must be at leats 18 years old</div>
</div>
</div>
<!-- Enter E-mail -->
<div class="form-group">
<label for="email" class="control-label"><span id="reqInfo">*</span> E-mail</label>
<input type="email" name="email" class="form-control" ng-model="register.user.email" ng-pattern="/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[\-;:&=\+\$,\w]+#)?[A-Za-z0-9\.\-]+|(?:www\.|[\-;:&=\+\$,\w]+#)[A-Za-z0-9\.\-]+)((?:\/[\+~%\/\.\w\-_]*)?\??(?:[\-\+=&;%#\.\w_]*)#?(?:[\.\!\/\\\w]*))?)/"
id="email" required="" placeholder="Example: mail#mail.net">
<div ng-messages="registerForm.email.$error" ng-show="registerForm.email.$touched" style="color:maroon" role="alert">
<div ng-message="required">Your valid e-mail is required</div>
</div>
<br>
<!-- Enter Username -->
<div class="form-group">
<label for="username" class="control-label"><span id="reqInfo">*</span> Username</label>
<input type="text" name="username" ng-minlength="5" ng-maxlength="20" class="form-control" ng-model="register.user.username"
ng-pattern="/^[A-Za-z0-9_]{1,32}$/" ng-minlength="7" id="username" required="" placeholder="Enter your username">
<div ng-messages="registerForm.username.$error" style="color:maroon" role="alert">
<div ng-message="minlength">Your Username must be between 7 and 20 characters long</div>
</div>
<br>
<!-- Enter Password -->
<div class="form-group">
<label for="password" class="control-label"><span id="reqInfo">*</span> Password</label>
<input type="password" name="password" class="form-control" ng-model="register.user.password" ng-minlength="7" id="password"
required="" placeholder="Enter your password">
<div ng-messages="registerForm.password.$error" style="color:maroon" role="alert">
<div ng-message="minlength">You Password must be at least 7 symbols long</div>
</div>
</div>
<!-- Register button -->
<div class="form-group">
<button class="btn btn-primary" type="submit" ng-disabled="!registerForm.name.$valid || !registerForm.age.$valid || !registerForm.email.$valid || !registerForm.username.$valid || !registerForm.password.$valid">Register</button>
</div>
<p>Fields with <span id="reqInfo">*</span> must be filled.</p>
</form>
</div>
Important is to know that I have being told explicitly to write it in ES6.
I have problem with the logic so look at my code and please fill it for me so I can use it and most important - learn it :S
Thank you so so much in advance!

I have implemented a directive for different kind of validations (sync Async), and it supports warning as well.
You may check it from
`https://plnkr.co/2WQHOo`
If this is what you needed and need more information, let me know I will try my best to answer.