What steps can be taken to ensure that AngularJS does not detach a form input's value from its model if it is invalid?

Question

What steps can be taken to ensure that AngularJS does not detach a form input's value from its model if it is invalid?

While working on a form implementation in AngularJS, I encountered a baffling behavior that has left me puzzled.

It seems that whenever I set ng-minlength=5 as an input attribute, AngularJS disconnects the value until it meets the length requirement.

This poses a problem for me as I want to display to the user the amount of content they have entered using user.lifestory.length.

Why does AngularJS exhibit this behavior? Is there a way to prevent Angular from unbinding the value when it's invalid?

<label for="lifeStory">Life story:<input name='lifeStory' type="text" ng-model='user.lifeStory' ng-minlength='5' required></input></label>

You can check out an example showcasing this issue here: http://jsfiddle.net/J67jm/3/

To observe the behavior I mentioned, try filling in the life story field.

javascript angularjs validation

Answer 1

Answer №1

If you need to access the current viewValue of lifeStory (not yet bound to model), you can utilize {{myForm.lifeStory.$viewValue}}. Here is a sample code that can help you solve your issue.

<span>Ensure your life story consists of at least 5 characters. You have input {{myForm.lifeStory.$viewValue.length}} characters.</span>

Take a look at this jsfiddle version - http://jsfiddle.net/J67jm/9/

Answer 2

If you need to access the current viewValue of lifeStory (not yet bound to model), you can utilize {{myForm.lifeStory.$viewValue}}. Here is a sample code that can help you solve your issue.

<span>Ensure your life story consists of at least 5 characters. You have input {{myForm.lifeStory.$viewValue.length}} characters.</span>

Take a look at this jsfiddle version - http://jsfiddle.net/J67jm/9/

Answer 3

Answer №2

When dealing with Angular, it appears that if the minlength is invalid, the framework may return a value of undefined. However, you have the ability to create your own validator directive for more control:

var myApp = angular.module('myApp',[]);

function MyCtrl($scope) {
  $scope.user = {};
  $scope.user.name = "";
  $scope.user.lifeStory = "";
}

myApp.directive('myMinlength', function (){ 
  return {
    require: 'ngModel',
    link: function(scope, elem, attr, ngModel) {
      var minlength = parseInt(attr.myMinlength); // Ensure integer

      ngModel.$parsers.unshift(function(value) {
        value = value || '';  // Prevent undefined values
        var valid = value.length >= minlength;
        ngModel.$setValidity('myMinlength', valid);
        return value;  // Always return the value
      });
    }
  };
});

Simply use this custom directive like so:

<input name='lifeStory' type="text" ng-model='user.lifeStory' my-minlength='5' required></input>

Here's an updated jsfiddle to see it in action.

It seems that ngRequired exhibits similar behavior and can be corrected using the same approach. Perhaps this applies to other validators as well?

I'm curious about the reasoning behind why the Angular team chose to handle the property in this manner...

Answer 4

When dealing with Angular, it appears that if the minlength is invalid, the framework may return a value of undefined. However, you have the ability to create your own validator directive for more control:

var myApp = angular.module('myApp',[]);

function MyCtrl($scope) {
  $scope.user = {};
  $scope.user.name = "";
  $scope.user.lifeStory = "";
}

myApp.directive('myMinlength', function (){ 
  return {
    require: 'ngModel',
    link: function(scope, elem, attr, ngModel) {
      var minlength = parseInt(attr.myMinlength); // Ensure integer

      ngModel.$parsers.unshift(function(value) {
        value = value || '';  // Prevent undefined values
        var valid = value.length >= minlength;
        ngModel.$setValidity('myMinlength', valid);
        return value;  // Always return the value
      });
    }
  };
});

Simply use this custom directive like so:

<input name='lifeStory' type="text" ng-model='user.lifeStory' my-minlength='5' required></input>

Here's an updated jsfiddle to see it in action.

It seems that ngRequired exhibits similar behavior and can be corrected using the same approach. Perhaps this applies to other validators as well?

I'm curious about the reasoning behind why the Angular team chose to handle the property in this manner...

Answer 5

Answer №3

You have the option to create a personalized validator directive that will handle the restoration of the $viewValue for you in the following manner:

.directive('customValidator', function () {
  return {
    restrict: 'A',
    require: 'ngModel',
    priority: 1, // ensuring postLink runs after other directives
    link: function (scope, element, attrs, modelCtrl) {
      modelCtrl.$parsers.push(function (viewValue) {
        return (viewValue === undefined) ? modelCtrl.$viewValue : viewValue;
      });
    }
  }
});

To implement it, simply use it like this:

<input name="personalInfo" type="text" ng-model="user.personalInfo" ng-minlength="5" required custom-validator></input>

Check out this sample plunker for reference: http://plnkr.co/edit/LbhF865FS8Zq5bQnpxnz?p=preview

Answer 6

You have the option to create a personalized validator directive that will handle the restoration of the $viewValue for you in the following manner:

.directive('customValidator', function () {
  return {
    restrict: 'A',
    require: 'ngModel',
    priority: 1, // ensuring postLink runs after other directives
    link: function (scope, element, attrs, modelCtrl) {
      modelCtrl.$parsers.push(function (viewValue) {
        return (viewValue === undefined) ? modelCtrl.$viewValue : viewValue;
      });
    }
  }
});

To implement it, simply use it like this:

<input name="personalInfo" type="text" ng-model="user.personalInfo" ng-minlength="5" required custom-validator></input>

Check out this sample plunker for reference: http://plnkr.co/edit/LbhF865FS8Zq5bQnpxnz?p=preview

What steps can be taken to ensure that AngularJS does not detach a form input's value from its model if it is invalid?

Answer №1

Answer №2

Answer №3

Similar questions

What could be causing the jQuery spritely animation to display an additional frame upon the second mouseenter event?

If the image is not found, deactivate the anchor or hyperlink

Place a material-ui React component at the center of a footer section

What is the reason for encodeURIComponent not encoding single quotes or apostrophes?

Input information into a JSON container

The console in React displays values, but fails to render them on the DOM

Dynamically setting the default selection in a dropdown menu

Why does React component still use old state when re-rendering?

Best approach for retrieving and adding a large number of images when dealing with slower connections

Mocha avoids running the test

The function of JQuery Validation successfully executes, but unfortunately, the page quickly refreshes and as a result, the submit function

Changing the background color of a page to match the background color of a button in React, which can be updated at any time

What is the formula to determine the sizes of grandchildren div containers?

Is AJAX.call functioning properly in every browser except for Firefox?

Determine whether the Bootstrap data-style attribute is enabled or disabled

How Express + Angular routing is leading to an endless loop and system crash

There is an issue showing up in the console: $(…).datepicker is not defined as a function

An elusive melody that plays only when I execute the play command

Leveraging Prisma Client alongside Supabase Edge Functions

Automatically hiding divs when clicked using HTML and CSS