How a component affects lifecycle of another component after removing in AngularJS ?
Last Updated :
13 Apr, 2023
In AngularJS, all components are connected with each i.e. they are often inter-dependent. So, If we are attempting to remove one component that can have a ripple effect on the overall lifecycle of another component. The specific effect directly depends on the specific type of components we are removing and how they are connected to each other.
When a component is being removed from a web application then it can affect the lifecycle of other components that were dependent on it in several ways. This is because components present in a web application can often rely on other components to provide the necessary functionality or data. If a component is removed without properly handling its dependencies (which are discussed below), then it can cause several errors or unexpected behavior in other components.
Let’s discuss some cases which could happen for component removal:
Case 1: When a component is being removed, then the first task of AngularJS will be to destroy that component and then remove it from the Document Object Model(DOM). If that component has child components then all those child components will also be destroyed at the time of the destruction of that parent component and removed from the DOM also.
Case 2: If a component that is being removed is already been subscribed to an event or observable from another component then that event or observable subscription should be unsubscribed before removing the component to prevent any memory leaks. If the subscription is not properly unsubscribed then it can continue to hold a reference to the already removed component and prevent it from being garbage collected which can create redundancies and garbage data records in the Database.
Case 3: If a removed component is referenced in the scope or state of another component then it can cause errors or unexpected behavior when that other component attempts to access the removed component. To prevent these types of errors, it is very important to properly manage component references and avoid referencing removed components.
Removing a component from a system’s database involves identifying all the dependencies of the component linked to other components and updating the rest of the system accordingly. Depending upon the types of systems, this work may involve updating configuration files, modifying codes, or making related changes to the database.
Approach: We will implement the same working code in two different approaches i.e. the output of both approaches are same but different methods are being used.
Approach 1: By using an event system that can notify dependent components of changes
Here, we will create an event system that components can subscribe to in order to be notified of changes i.e. when a component is being removed, it will able to trigger an event that notifies any dependent components to update or remove themselves about the remove event.
Example: In the following example, we will create an event system using the EventTarget API. “Component A” has a button that can trigger a custom event called component-a-removed when it is clicked by the user. On the other hand, “Component B” listens for this event using addEventListener and has a callback function that makes updating its content when the event is triggered.
HTML
<!DOCTYPE html>
<html>
<head>
<title>
How a component affects lifecycle of
another component after removing?
</title>
</head>
<body>
<h1 style="color:green;">
GeeksforGeeks
</h1>
<h3 style="color:red;">
Component Removing
</h3>
<div id="component-a">
<button id="remove-component-a">
Remove Component A
</button>
</div>
<div id="component-b">
<p>Component B</p>
</div>
<script>
// Creating the event system
const eventSystem = new EventTarget();
// Component A related events
const componentA =
document.querySelector('#component-a');
const removeButton =
document.querySelector('#remove-component-a');
removeButton.addEventListener('click', () => {
// Defining trigger remove event
const removeEvent = new Event('component-a-removed');
eventSystem.dispatchEvent(removeEvent);
componentA.remove();
});
// Component B related events
const componentB = document.querySelector('#component-b');
const removeComponentA = () => {
componentB.innerHTML =
'<p>Component B (Component A removed)</p>';
};
eventSystem.addEventListener('component-a-removed',
removeComponentA);
</script>
</body>
</html>
|
Output:
Approach2: By using a state management library to handle dependencies
For this approach, we will use any state management libraries, like “Redux” to handle dependencies between components. When a component is being removed then, we will update the global state to reflect the changes and any dependent components can update themselves accordingly based on the new state.
Example: In the following example, we will create a Redux store with an initial state that includes a flag indicating whether “Component A” exists or not. When the “Remove Component A” button is clicked by the user, then it will dispatch a removeComponentA action that updates the state to set componentAExists to false. After that, “Component B” subscribes to the store using the store.subscribe and has a callback function (similar to approach1) that makes necessary updates on its content based on the new state.
HTML
<!DOCTYPE html>
<html>
<head>
<title>
How a component affects lifecycle of
another component after removing?
</title>
<script src=
</script>
</head>
<body>
<h1 style="color:green;">
GeeksforGeeks
</h1>
<h3 style="color:red;">
Component Removing
</h3>
<div id="component-a">
<button id="remove-component-a">
Remove Component A
</button>
</div>
<div id="component-b">
<p>Component B</p>
</div>
<script>
// Defining initial state
const initialState = {
componentAExists: true,
};
// Defining the actions
const REMOVE_COMPONENT_A = 'REMOVE_COMPONENT_A';
const removeComponentA = () => ({ type: REMOVE_COMPONENT_A });
// Defining the reducer
const reducer = (state = initialState, action) => {
switch (action.type) {
case REMOVE_COMPONENT_A:
return { ...state, componentAExists: false };
default:
return state;
}
};
// Creating the data store
const store = Redux.createStore(reducer);
// Component A related events
const componentA = document.querySelector('#component-a');
const removeButton =
document.querySelector('#remove-component-a');
removeButton.addEventListener('click', () => {
store.dispatch(removeComponentA());
componentA.remove();
});
// Component B related events
const componentB =
document.querySelector('#component-b');
const updateComponentB = () => {
const state = store.getState();
if (!state.componentAExists) {
componentB.innerHTML =
'<p>Component B (Component A removed)</p>';
}
};
store.subscribe(updateComponentB);
</script>
</body>
</html>
|
Output:
Note: The output for both approaches will be the same.
Share your thoughts in the comments
Please Login to comment...