Web Develpers era: lifecycle hooks in vuejs

Ans: Lifecycle hooks are functions that every Vue instance runs through. Each vue has eight lifecycle hooks. An instance of js

Before Create - This is the first lifecycle hook that is called when a Vue instance has been created.
Created - It's called immediately after the 'Before creates' hook, but the Vue instance has already set initial properties, data, etc.
Before mount - invoked right before the instance is mounted on the DOM. The template has been completed at this time.
Mounted - This is the name given to the template once it has been filled with data and is fully functional.
Before Updated - When any changes to data require the DOM to be changed, this method is called before the update.
Updated - It's called after the DOM has been updated.
Before destroy - It's a location where you can clean up your resources before terminating the Vue instance.
Destroyed - When all Vue instances have been destroyed, this method is called. When you call the destruct method on an object in code, it will be activated.

<head>
    <title>My Vue.js App</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.14/dist/vue.min.js"></script>
  </head>
  <body>
    <div id="app">
      <h1>{{ message }}</h1>
      <button @click="incrementCount">{{ count }}</button>
    </div>
  </body>
  <script>
    new Vue({
      el: '#app',
      data: {
        count: 0,
      },
      computed: {
    message() {
      return `The count is ${this.count}.`;
    },
  },
  beforeCreate() {
    console.log("beforeCreate hook called.");
  },
  created() {
    console.log("created hook called.");
  },
  beforeMount() {
    console.log("beforeMount hook called.");
  },
  mounted() {
    console.log("mounted hook called.");
  },
  beforeUpdate() {
    console.log("beforeUpdate hook called.");
  },
  updated() {
    console.log("updated hook called.");
  },
  beforeDestroy() {
    console.log("beforeDestroy hook called.");
  },
  destroyed() {
    console.log("destroyed hook called.");
  },
  methods: {
    incrementCount() {
      this.count++;
    },
  },
  watch: {
    count(newVal, oldVal) {
      console.log(`count changed from ${oldVal} to ${newVal}.`);
    },
  },
    });
  </script>
  

before dom -create

after dom - mount

updated: any update of element

In Vue.js, the created and mounted lifecycle hooks are two important methods that are executed at different stages of a Vue component's lifecycle. Here are the main differences between created and mounted:

Execution Timing:
- created: The created hook is called when the Vue component has been created, and the component's data and methods have been initialized. However, the component's template has not been rendered or mounted to the DOM yet.
- mounted: The mounted hook is called when the Vue component's template has been compiled and mounted to the DOM. It is executed after the initial rendering of the component.
DOM Access:
- created: In the created hook, you can access the component's data, methods, and computed properties. However, you cannot access or manipulate the DOM elements rendered by the component since they have not been mounted yet.
- mounted: In the mounted hook, you have access to the component's DOM elements, and you can manipulate the DOM, attach event listeners, or interact with other JavaScript libraries that require DOM presence.
Use Cases:
- created: The created hook is commonly used to initialize component properties, set up event listeners or watchers, fetch initial data from an API, or perform any necessary setup logic before the component is mounted.
- mounted: The mounted hook is often used when you need to perform DOM-related operations, such as initializing third-party libraries, accessing DOM elements for measurements or calculations, or making changes to the DOM after the component has been rendered.

It's important to note that these hooks are just two of many lifecycle hooks available in Vue.js. Each lifecycle hook serves a specific purpose and provides developers with the ability to perform actions at different stages of a component's lifecycle. Understanding the lifecycle hooks helps you control the behavior and interaction of your Vue components effectively.

In Vue.js, the mounted and updated lifecycle hooks are two methods that are called at different stages of a component's lifecycle. Here are the main differences between mounted and updated:

Execution Timing:
- mounted: The mounted hook is called once when the component's template has been compiled and mounted to the DOM for the first time. It occurs after the initial rendering of the component.
- updated: The updated hook is called whenever a reactive dependency of the component has changed, and the component needs to re-render. It occurs after the component has been updated and re-rendered.
DOM Access:
- mounted: In the mounted hook, you have access to the component's DOM elements. You can manipulate the DOM, attach event listeners, or interact with other JavaScript libraries that require DOM presence.
- updated: In the updated hook, you can also access and manipulate the component's DOM elements. However, you need to be cautious to avoid causing an infinite update loop, as any changes made to the DOM during the updated hook may trigger further updates.
Number of Executions:
- mounted: The mounted hook is executed only once when the component is first mounted to the DOM.
- updated: The updated hook can be called multiple times during the lifecycle of a component, whenever a reactive dependency of the component changes and triggers a re-render.
Use Cases:
- mounted: The mounted hook is commonly used for performing initial setup tasks that require access to the DOM, such as initializing third-party libraries, fetching data from an API, setting up event listeners, or performing calculations involving the component's rendered elements.
- updated: The updated hook is useful when you need to perform additional actions after a component has re-rendered due to changes in its reactive data. This could include updating the DOM based on new data, making API calls based on updated input values, or interacting with other components or libraries after a change has occurred.

Both mounted and updated are important hooks for managing component lifecycle and interactivity in Vue.js. Understanding their differences allows you to leverage them effectively to control the behavior and synchronization of your components.

difference between updated and destroyed

In Vue.js, the updated and destroyed lifecycle hooks are two methods that are called at different stages of a component's lifecycle. Here are the main differences between updated and destroyed:

Execution Timing:
- updated: The updated hook is called after a component has been re-rendered due to changes in its reactive dependencies. It is executed after the component has updated and the virtual DOM has been patched with the changes.
- destroyed: The destroyed hook is called when a component is being destroyed and removed from the DOM. It is the last hook called before the component is completely removed.
DOM Access:
- updated: In the updated hook, you have access to the component's DOM elements. You can perform operations on the updated DOM, such as manipulating elements, applying animations, or interacting with other libraries.
- destroyed: In the destroyed hook, the component's DOM elements are still accessible. However, it's important to note that the component is in the process of being destroyed, and any further interactions with the DOM should be avoided.
Number of Executions:
- updated: The updated hook can be called multiple times during the lifecycle of a component, whenever a reactive dependency of the component changes and triggers a re-render.
- destroyed: The destroyed hook is called only once when the component is being destroyed. It signifies that the component is no longer active and is being removed from the DOM.
Use Cases:
- updated: The updated hook is commonly used for performing actions after the component has re-rendered, such as updating the DOM based on new data, interacting with other components or libraries, or triggering animations and effects.
- destroyed: The destroyed hook is useful for cleaning up resources or performing necessary cleanup tasks before a component is completely removed from the DOM. This could include removing event listeners, canceling timers or subscriptions, or releasing any resources allocated during the component's lifecycle.

Understanding the differences between the updated and destroyed hooks helps in managing the component lifecycle effectively and ensuring proper cleanup and interaction with the DOM at different stages of a component's existence.

In the context of web development, the terms "mounted" and "created" are typically associated with frameworks such as Vue.js or React.js. Let's discuss them in the context of Vue.js.

In Vue.js, the lifecycle of a component consists of various stages. The "created" stage occurs when the component is initialized, and its data and methods are set up. This stage is triggered before the component is added to the DOM (Document Object Model). During the "created" stage, you can perform tasks such as initializing data, setting up watchers, or making API requests.

On the other hand, the "mounted" stage occurs when the component is added to the DOM and all its child components have also been mounted. At this point, the component is accessible in the DOM and you can interact with its rendered elements. You can use this stage to manipulate the DOM, set up event listeners, or perform additional initialization tasks that require access to the DOM.

In summary, the "created" stage happens before the component is mounted to the DOM, while the "mounted" stage occurs after the component is mounted and accessible in the DOM.

created: vue instance, not dom loads

after before create only dom loads,

when everything installed mounted works

Web Develpers era

lifecycle hooks in vuejs

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