Methods vs Computed Properties in Vue

In Vue.js, methods and computed properties are indeed similar in that they both allow you to create dynamic content based on your component’s data. However, they are used for different purposes and have distinct characteristics:

Methods

• Definition: Methods are functions defined in the `methods` option of a Vue component.
• Usage: You call a method directly from the template or other parts of your component.
• Reactivity: Methods are not cached. Every time you call a method, it will be executed again, regardless of whether the underlying data has changed.

Example:

<template>
    <div>
        <button @click="updateMessage">Update Message</button>
        <p>{{ getMessage() }}</p>
    </div>
</template>
<script>
export default {
    data() {
        return {
            message: 'Hello, Vue!'
        };
    },
    methods: {
        getMessage() {
            // Method execution
            return this.message + ' Updated!';
        },
        updateMessage() {
            this.message = 'Hello, Vue Updated!';
        }
    }
};
</script>

Computed Properties

• Definition: Computed properties are defined in the `computed` option of a Vue component.
• Usage: Computed properties are accessed as if they were regular data properties, but they are actually functions.
• Reactivity: Computed properties are cached based on their reactive dependencies. They will only recompute when one of their dependencies changes, making them more efficient than methods in scenarios where you need to access the computed value multiple times.

Example:

<template>
    <div>
        <button @click="updateMessage">Update Message</button>
        <p>{{ computedMessage }}</p>
    </div>
</template>
<script>
export default {
    data() {
        return {
            message: 'Hello, Vue!'
        };
    },
    computed: {
        computedMessage() {
            // Computed property execution
            return this.message + ' Updated!';
        }
    },
    methods: {
        updateMessage() {
            this.message = 'Hello, Vue Updated!';
        }
    }
};
</script>

Key Differences

1. Caching

Methods: Always recomputed when called.
Computed: Cached and only recomputed when dependencies change.

2. Performance

Methods: Can be less performant if the method involves complex calculations and is called multiple times.
Computed: More efficient for dependent calculations, especially when used multiple times in a template.

3. Usage Context

Methods: Ideal for actions or operations that do not need to be cached.
Computed: Ideal for derived state that depends on reactive data and benefits from caching.

In summary, if you have a value that depends on reactive data and is used multiple times, it’s better to use a computed property. For actions or one-off operations that do not need to be cached, methods are more appropriate.