How to read value in textbox that already put in textbox

I create remeber me functionality so if In local storage any value stored ,by default that value display in textbox.
now problem is that if i click on submit without any changes in textbox then i didn’t get any value from the textbox means it takes blank value but i ntext boxc already value have.

code that i used

<ion-content class="home" padding>
    <form [ngFormModel]="authForm" (ngSubmit)="onSubmit(authForm.value)">
        <ion-item [class.error]="!username.valid">
            <ion-label floating>Username</ion-label>
            <ion-input type="text" value={{userValue}} [ngFormControl]="username"></ion-input>         
        </ion-item>
        <div *ngIf="username.hasError('required') && username.touched" 
            class="error-box">*Username is required!</div>
        <div *ngIf="username.hasError('minlength') && username.touched" 
            class="error-box">*Minimum username length is 3!</div>            
                             
        <ion-item [class.error]="!password.valid">
            <ion-label floating>Password</ion-label>
            <ion-input type="password" value = {{pwdValue}} [ngFormControl]="password" ></ion-input>
        </ion-item>
        <div *ngIf="password.hasError('required') && password.touched" 
            class="error-box">*Password is required</div>    
        <div *ngIf="password.hasError('minlength') && password.touched" 
            class="error-box">*Minimum password length is 3!</div>        
        <br/><br/> 
        <ion-item>
            <ion-label>Remember Me</ion-label>
            <ion-checkbox ngmodel='isChecked' checked ={{isChecked}}></ion-checkbox>
        </ion-item>
        <br/><br/> 
        <button type="submit" class="custom-button" block>Submit</button>
    </form>
</ion-content>


constructor(private navController: NavController, private fb: FormBuilder,private service: WebService) {
        this.authForm = fb.group({  
            'username': ['', Validators.compose([Validators.required, Validators.minLength(3)])],
            'password': ['', Validators.compose([Validators.required, Validators.minLength(3)])]
        });

        this.username = this.authForm.controls['username'];     
        this.password = this.authForm.controls['password']; 
}

here i tried to access username value

console.log(“username”,this.username.value);

I’m surprised this template works at all with all the unquoted attribute values.

but in my case it’s not works…this is worked when i write username manually it will work

but when i put value programetically and click on submit button get null value