How to make 'submit' button disabled?

Question

As seen in this Angular example, there is a way to disable a button until the whole form is valid:

<button type="submit" [disabled]="!ngForm.valid">Submit</button>

in Angular 2.x.x , 4, 5 ...

<form #loginForm="ngForm">
    <input type="text" required> 
    <button  type="submit"  [disabled]="loginForm.form.invalid">Submit</button>
</form>

.html

<form [formGroup]="contactForm">

<button [disabled]="contactForm.invalid"  (click)="onSubmit()">SEND</button>

.ts

contactForm: FormGroup;

Here is a working example (you'll have to trust me that there's a submit() method on the controller - it prints an Object, like {user: 'abc'} if 'abc' is entered in the input field):

<form #loginForm="ngForm" (ngSubmit)="submit(loginForm.value)">
    <input type="text" name="user" ngModel required>
    <button  type="submit"  [disabled]="loginForm.invalid">
        Submit
    </button>
</form>

As you can see:

• don't use loginForm.form, just use loginForm
• loginForm.invalid works as well as !loginForm.valid
• if you want submit() to be passed the correct value(s), the input element should have name and ngModel attributes

Also, this is when you're NOT using the new FormBuilder, which I recommend. Things are very different when using FormBuilder.

Form validation is very much straight forward in Angular 2

Here is an example,

<form (ngSubmit)="onSubmit()" #myForm="ngForm">

 <div class="form-group">
  <label for="firstname">First Name</label>
  <input type="text" class="form-control" id="firstname" 
   required [(ngModel)]="firstname" name="firstname">
 </div>

 <div class="form-group">
  <label for="middlename">Middle Name</label>
  <input type="text"  class="form-control" id="middlename" 
   [(ngModel)]="middlename" name="middlename">
 </div>

 <div class="form-group">
  <label for="lastname">Last Name</label>
  <input type="text"  class="form-control" id="lastname" 
   required minlength = '2' maxlength="6" [(ngModel)] = "lastname" name="lastname">
 </div>

 <div class="form-group">
  <label for="mobnumber">Mob Number</label>
  <input type="text"  class="form-control" id="mobnumber"  
   minlength = '2' maxlength="10" pattern="^[0-9()\-+\s]+$" 
   [(ngModel)] = "mobnumber" name="mobnumber">
 </div>

 <button type="submit" [disabled]="!myForm.form.valid">Submit</button>

</form>

Check this plunker for demo

More info

This worked for me.

.ts

newForm : FormGroup;

.html

<input type="button" [disabled]="newForm.invalid" />