This article is about fixing Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular
  • 13-Feb-2023
Lightrun Team
Author Lightrun Team
This article is about fixing Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular

Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular

Lightrun Team
Lightrun Team

Explanation of the problem

Problem Description

The current behavior of the checkbox input with the [ngModel] binding and (ngModelChange) event handler is not functioning as expected. The checkbox only reflects the model value when it is first rendered, but then becomes equivalent to a checkbox without a binding. The logic in the onChanges function is not being run, and the view is not being updated to reflect the current value of the model.

Code Example

<input type="checkbox" [ngModel]="foo" (ngModelChange)="onChanges()" />
<input type="checkbox" (onChanges)="onChanges()" />

Environment Details

The issue has been observed on Mac OS X Sierra and is being developed using IntelliJ IDEA. The Angular version used is 2.2.0, and the code is written in TypeScript 2.0.2. The issue has been reported to occur on all browsers.


The [ngModel] binding should always reflect the current value of the model and the logic in the onChanges function should run. The expected behavior is that the view should be updated to reflect the model’s current value. The minimal reproduction of the problem can be found at the following URL:

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Problem solution for Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular

The solution to the checkbox [ngModel] not reflecting the model value when updated in (onModelChange) in Angular can be achieved through a couple of workarounds. One of the most commonly used solutions is by using a custom value accessor. This involves creating a custom component that implements the ControlValueAccessor interface and wraps the native checkbox element.

Another solution is by using the NgModelChange directive with a setTimeout function. This works by wrapping the logic inside the (ngModelChange) function in a setTimeout function, which will then wait until the end of the current JavaScript execution before executing the logic. This allows Angular to detect the change to the checkbox value before running the logic inside the (ngModelChange) function.

It’s important to note that while these solutions resolve the issue, they may cause other unintended side effects and it’s recommended to properly test and evaluate their use in different environments and applications.

Other popular problems with angular angular

Problem: Routing in Angular

One of the most common issues with Angular is with routing. Angular’s routing system allows you to define specific paths in your application that correspond to specific components. However, when multiple routes are defined, it can be difficult to manage and keep track of the different routes in the application. This can result in unexpected behavior, such as incorrect navigation or broken links.


To overcome this issue, developers can use a routing library, such as Angular UI Router, which provides a more robust and flexible routing system. This library allows developers to define nested routes, which can be useful when building complex applications. Additionally, the library provides a number of tools to manage routes, such as state transition hooks and state-based navigation.

// Defining a nested state in Angular UI Router
  .state('parent', {
    url: '/parent',
    template: '<div ui-view></div>',
    abstract: true
  .state('parent.child', {
    url: '/child',
    template: '<div>This is a child state</div>'

Problem: Change Detection in Angular

Another common issue in Angular is with change detection. Angular uses a change detection mechanism to track changes in the application’s data and update the view accordingly. However, when working with large and complex applications, the change detection mechanism can become slow and inefficient, resulting in poor performance.


To improve change detection performance, developers can use strategies such as OnPush change detection, which only performs change detection on a component when its inputs have changed. Additionally, developers can also use the NgZone class to manually control when change detection occurs in the application.

// Using OnPush change detection in Angular
  selector: 'app-example',
  template: '...',
  changeDetection: ChangeDetectionStrategy.OnPush
export class ExampleComponent {
  // ...

Problem: Managing Forms in Angular

Forms are a common requirement in many web applications, and Angular provides a comprehensive system for managing forms. However, this system can be complex and difficult to work with, especially when dealing with dynamic forms or custom validation.


To simplify form management, developers can use libraries such as Angular Reactive Forms, which provide a more intuitive and flexible approach to working with forms. These libraries allow developers to easily create dynamic forms and perform custom validation, without having to write complex code.
// Using Angular Reactive Forms to create a form
this.form ={
  name: ['', Validators.required],
  email: ['', [Validators.required,]]

A brief introduction to angular angular

Angular is a widely-used JavaScript framework for building complex, single-page applications. It was developed and is maintained by Google and is designed to make building scalable, high-performance applications easy and straightforward. Angular is based on the component-based architecture and follows the Model-View-Controller (MVC) pattern, which helps developers to create structured, reusable and maintainable code.

One of the key benefits of Angular is its ability to simplify the development of dynamic user interfaces. Angular uses two-way data binding to keep the model and view in sync, reducing the amount of code required to handle updates to the UI. Angular also provides a rich set of built-in directives, services, and libraries for handling common tasks like HTTP requests, form validation, and animation, making it an ideal choice for developing complex applications. Additionally, Angular has a large community of developers and a wealth of online resources, which makes it easy to find help and learn new techniques.

Most popular use cases for angular angular

  1. Building Dynamic Web Applications: Angular Angular is a powerful framework that can be used to build complex and dynamic web applications. With its robust set of features and libraries, Angular Angular allows developers to build applications that can handle large amounts of data, interactivity, and real-time updates. This makes it an ideal choice for applications like e-commerce platforms, social networks, and online marketplaces.
  2. Enhancing User Experience: Angular Angular provides a wide range of tools and libraries that can be used to create an exceptional user experience. With its two-way data binding, Angular Angular makes it easy to keep the user interface in sync with the underlying data model. This results in a more intuitive and responsive user experience, which can significantly improve user engagement and satisfaction.
  3. Streamlining Development Workflow: Angular Angular provides a structured and organized approach to web development, which makes it easy for teams to collaborate and build applications efficiently. Its modular architecture and reusable components can significantly reduce development time and help to minimize code duplication. Additionally, Angular Angular provides tools for testing, debugging, and performance optimization that can help to streamline the development workflow and improve the overall quality of the application.
import { Component } from '@angular/core';

  selector: 'app-root',
  template: `
export class AppComponent {
  title = 'Welcome to Angular Angular';
  description = 'A powerful framework for building web applications';

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