Angular is a well-known web development framework that offers various features and functionality. One of its most essential features is the data binding mechanism, which allows the front-end code to interact with the back-end data. Two commonly used directives are change and ngModelChange, and they often get confused with each other. In this blog post, we’ll discuss the difference between these two directives, their usage, and which one is more performant.
Difference Between Change And ngModelChange in Angular:
The “change” and “ngModelChange” directives are similar but have significant differences.
change Directive
The “change” directive fires the event whenever the element value changes, regardless of user interaction.
Usage
The “change” directive is often used when you want to detect any programmatic change made to the element value. It is commonly used in scenarios such as resetting the value of an element, form validation, and other similar features. For instance, suppose you want to track the number of times an input field value is changed programmatically. In that case, you can use the “change” directive.
code snippet
<input type="text" [(ngModel)]="name" (change)="onNameChange($event)">
ngModelChange Directive
On the other hand, “ngModelChange” directive triggers the event only when a user changes the element value through direct interaction. It means that the “ngModelChange” directive only responds to user events, not changes made programmatically.
Usage
The “ngModelChange” directive is used to track user interaction with the element. It is often used in form controls to perform actions such as updating back-end data, performing validations, or displaying some feedback message to the user. An example of using “ngModelChange” directive can be seen when a user needs to change their profile password. The directive would listen for user interaction with the input field and thus perform the designated update action.
Code Snippet
<input type="password" [(ngModel)]="password" (ngModelChange)="onPasswordChange($event)">Performance and Limitations of ngModelChange:
While the “ngModelChange” directive can provide valuable real-time insights into user interactions, it’s important to use this tool judiciously due to a couple of performance-related considerations. First, improper or excessive use of “ngModelChange” can lead to a ‘Maximum call stack size exceeded’ error. This issue occurs when there’s a circular event loop, i.e., an ngModelChange event triggers another function that, in turn, modifies the model and triggers the ngModelChange again, leading to an infinite loop.
Moreover, when using Angular forms, especially with large forms or complex validations, “ngModelChange” may not be the most performant choice. Each change to the form’s value triggers the directive, which can lead to a substantial performance hit due to the overhead of executing code for every user interaction, even minor ones. It is advisable to use other form-related directives or methods to handle changes and validations more efficiently, such as using ‘valueChanges’ on form controls or debouncing the changes, which can limit the number of calls being made.
Conclusion
In conclusion, the difference between “change” and “ngModelChange” directives is their firing mechanism, with the former firing events on all changes and the latter only on events caused by direct user interaction. The “change” directive is often used in scenarios that track programmatic updates, while “ngModelChange” is used for user interactions with the element. And finally, “ngModelChange” is more performant, making it the preferred directive for most Angular applications. If you want more in-depth Angular content, please follow our blog for more!