Angular 4 default radio button checked by default
Solution 1
You can use [(ngModel)]
, but you'll need to update your value
to [value]
otherwise the value is evaluating as a string. It would look like this:
<label>This rule is true if:</label>
<label class="form-check-inline">
<input class="form-check-input" type="radio" name="mode" [value]="true" [(ngModel)]="rule.mode">
</label>
<label class="form-check-inline">
<input class="form-check-input" type="radio" name="mode" [value]="false" [(ngModel)]="rule.mode">
</label>
If rule.mode
is true, then that radio is selected. If it's false, then the other.
The difference really comes down to the value
. value="true"
really evaluates to the string 'true', whereas [value]="true"
evaluates to the boolean true.
Solution 2
We can use [(ngModel)] in following way and have a value selection variable radioSelected
app.component.html
<div class="text-center mt-5">
<h4>Selected value is {{radioSel.name}}</h4>
<div>
<ul class="list-group">
<li class="list-group-item" *ngFor="let item of itemsList">
<input type="radio" [(ngModel)]="radioSelected" name="list_name" value="{{item.value}}" (change)="onItemChange(item)"/>
{{item.name}}
</li>
</ul>
</div>
<h5>{{radioSelectedString}}</h5>
</div>
app.component.ts
import {Item} from '../app/item';
import {ITEMS} from '../app/mock-data';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
title = 'app';
radioSel:any;
radioSelected:string;
radioSelectedString:string;
itemsList: Item[] = ITEMS;
constructor() {
this.itemsList = ITEMS;
//Selecting Default Radio item here
this.radioSelected = "item_3";
this.getSelecteditem();
}
// Get row item from array
getSelecteditem(){
this.radioSel = ITEMS.find(Item => Item.value === this.radioSelected);
this.radioSelectedString = JSON.stringify(this.radioSel);
}
// Radio Change Event
onItemChange(item){
this.getSelecteditem();
}
}
Sample Data for Listing
export const ITEMS: Item[] = [
{
name:'Item 1',
value:'item_1'
},
{
name:'Item 2',
value:'item_2'
},
{
name:'Item 3',
value:'item_3'
},
{
name:'Item 4',
value:'item_4'
},
{
name:'Item 5',
value:'item_5'
}
];
Solution 3
if you're using reactive forms then you can use the following way. consider the following example.
in component.html
`<p class="mr-3"> Require Shipping:
<input type="radio" class="ml-2" value="true" name="requiresShipping"
id="requiresShipping" formControlName="requiresShipping">
Yes
<input type="radio" class="ml-2" value="false" name="requiresShipping"
id="requiresShipping" formControlName="requiresShipping">
No
</p>`
in component.ts
`
export class ClassName implements OnInit {
public yourForm: FormGroup
constructor(
private fromBuilder: FormBuilder
) {
this.yourForm= this.fromBuilder.group({
requiresShipping: this.fromBuilder.control('true'),
})
}
}
`
now you will get the default selected radio button.
Jotan
Updated on November 28, 2021Comments
-
Jotan over 2 years
I'm trying to mark as a default a radiobutton depending on the value I get from my object, it can be True or False. What could I do to mark as a default radiobutton depending on the option?
<label>This rule is true if:</label> <label class="form-check-inline"> <input class="form-check-input" type="radio" name="mode" value="true" [(ngModel)]="rule.mode"> all of the following conditions are true </label> <label class="form-check-inline"> <input class="form-check-input" type="radio" name="mode" value="false" [(ngModel)]="rule.mode"> at least one of the following conditions is true </label>
I have the true or false set in
rule.mode
. -
Buminda over 6 yearsThanks , you saved my day !!
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Ajitesh almost 6 yearsIn case, you still want the value to use 'true' as string and checked by default, you will need to set the value of rule.mode as true as default value.
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L. Kvri almost 6 yearsIt looks like you're using ngModel on the same form field as formControlName. Support for using the ngModel input property and ngModelChange event with reactive form directives has been deprecated in Angular v6 and will be removed in Angular v7. For more information on this, see our API docs here: angular.io/api/forms/FormControlName#use-with-ngmodel
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Rich almost 6 yearsThanks for the answer and explanation. I was doing the same thing only the property for my radio button was type number. Without property binding on value it was being evaluated as a string instead of a number and the default radio button wasn't being checked.