javascript / intermediate
Snippet
Validating Asynchronous Data
Async validators allow you to perform validation logic that requires a remote call, such as checking if a username is already taken. Setting 'updateOn: blur' optimizes performance by only running the check when the user leaves the field.
snippet.js
javascript
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this.form = new FormGroup({username: new FormControl('', {asyncValidators: [this.uniqueUsernameValidator.bind(this)],updateOn: 'blur'})});
angular
Breakdown
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asyncValidators: [...]
A list of functions that return a Promise or Observable for validation.
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updateOn: 'blur'
Configures the control to only run validators when the input loses focus.