Composition API实现逻辑复用

• 抽离逻辑代码到一个函数
• 函数命名约定为useXxxx格式（react Hooks也是）
• 在setup中去引用这个函数

如下经典鼠标位置例子：

// useMousePosition.ts
import { onMounted, onUnmounted, ref } from "vue";

const useMousePosition = () => {
    const x = ref(0);
    const y = ref(0);

    function mousemoveHandler(e: MouseEvent) {
        x.value = e.pageX;
        y.value = e.pageY;
    }

   onMounted(() => window.addEventListener('mousemove', mousemoveHandler));
   onUnmounted(() => window.removeEventListener('mousemove', mousemoveHandler));

    return { x, y }
}
export default useMousePosition;

// index.vue
<template>
    <div>
        position - x: {{ x }}, y: {{ y }}
    </div>
</template>

<script lang="ts">
import useMousePosition from './useMousePosition';

export default {
    setup() {
        const { x, y } = useMousePosition()
        return {
            x,
            y
        }
    }
}
</script>