What is the `beforeCreate` hook used for?

VueJunior~1 min read

beforeCreate is the first lifecycle hook of a Vue component. It is called before anything else, even before reactivity, props, computed properties, and methods are initialized.

In other words:

beforeCreate is the moment the component is just starting to be created, but it doesn't have access yet to either data or props.

What happens during beforeCreate?

At this stage:

Vue has not created the reactive data (data) yet
props are not available yet
methods are not bound to the instance yet
computed and watch are not initialized yet
only the bare component instance is available

What can and cannot be done in beforeCreate?

What you CANNOT do:

The hook has no access to:

this.dataProperty
this.someMethod()
this.someComputed
this.someProp

All of them will be undefined.

What you can do:

1. Set up global variables

For example, binding DI (dependency injection) in large applications.

2. Connect plugins that must run before everything else

3. Debugging

The hook is useful for analyzing the initialization process.

4. Modify the instance before Vue applies reactivity

Example of the behavior

export default {
  data() {
    return { msg: "Hello" };
  },

  beforeCreate() {
    console.log(this.msg);      // undefined
    console.log(this.$data);    // undefined
    console.log(this.$props);   // undefined
  },

  created() {
    console.log(this.msg);      // "Hello"
  }
}

When can `beforeCreate` actually be used?

In a real application it's rarely needed. But there are cases:

1. Initializing early dependencies

For example, libraries that must connect before reactivity is created.

2. Internal plugins and mixins

Plugins need an "early entry point".

3. Dependency injection (especially in Vue 2)

4. Optimizations when creating a large number of small components

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