When it comes to New Directions in Vue Compiler Optimization, many developers only scratch the surface at the API call level. This article attempts to discuss the real-world problems and solutions you'll encounter from a production environment perspective.

Basic Principles

Let's start with the basic implementation:

import { ref, computed, watch, onMounted } from "vue";

export default {
  setup() {
    const count = ref(0);
    const doubled = computed(() => count.value * 2);

    watch(count, (newVal, oldVal) => {
      console.log(`count: ${oldVal} -> ${newVal}`);
    });

    onMounted(() => {
      console.log("Component mounted");
    });

    return { count, doubled };
  },
};

This code demonstrates the basic usage. In real projects, you also need to consider error handling and edge cases.

Advanced Features

Building on this foundation, we can further optimize:

import { ref, computed, watch, onMounted } from "vue";

export default {
  setup() {
    const count = ref(0);
    const doubled = computed(() => count.value * 2);

    watch(count, (newVal, oldVal) => {
      console.log(`count: ${oldVal} -> ${newVal}`);
    });

    onMounted(() => {
      console.log("Component mounted");
    });

    return { count, doubled };
  },
};

This pattern is very practical in large projects and can significantly reduce maintenance costs.

Project Practice

In real projects, the usage gets more complex:

import { ref, computed, watch, onMounted } from "vue";

export default {
  setup() {
    const count = ref(0);
    const doubled = computed(() => count.value * 2);

    watch(count, (newVal, oldVal) => {
      console.log(`count: ${oldVal} -> ${newVal}`);
    });

    onMounted(() => {
      console.log("Component mounted");
    });

    return { count, doubled };
  },
};

Through this approach, both testability and scalability of the code are improved.

Best Practices

Here is a complete example:

import { ref, computed, watch, onMounted } from 'vue'

export default {
  setup() {
    const count = ref(0)
    const doubled = computed(() => count.value * 2)