如何将此动态ajax函数转换为vue js

<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
    new Vue({
        el: '#app',
        data: {
            responseData: null
        },
        methods: {
            fetchData: function() {
                // 在这里编写动态ajax函数的代码
                // 将获取到的数据赋值给responseData
            }
        },
        mounted: function() {
            this.fetchData();
        }
    });
</script>

<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script>
<script>
    new Vue({
        el: '#app',
        data: {
            responseData: null
        },
        methods: {
            fetchData: function() {
                axios.get('https://example.com/api/data')
                    .then(response => {
                        this.responseData = response.data;
                    })
                    .catch(error => {
                        console.log(error);
                    });
            }
        },
        mounted: function() {
            this.fetchData();
        }
    });
</script>

<div id="app">
    <p>{{ responseData }}</p>
</div>