21.VUE学习之-操作data里的数组变异方法push&unshit&pop&shift的实例应用讲解

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <!--<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>-->
    <script type="text/javascript" src="../js/vue.js"></script>
</head>
<body>
<div id="hdcms">
    <li v-for="v in comments">
        {{v.content}}
    </li>
    <textarea v-model="current_content" cols="30" rows="10"></textarea><br>
    <button v-on:click="push('end')">发表到后面</button>
    <button v-on:click="push('pre')">发表到前面</button>
    <br>
    <button v-on:click="del('last')">删除最后一条评论</button>
    <button v-on:click="del('first')">删除第一条评论</button>
</div>
<script>
    var app = new Vue({
        el: '#hdcms',
        data: {
            //当前用户输入内容
            current_content: '',
            comments: [
                {content: '后盾人'},
                {content: '向军老师'},
            ]
        },
        methods: {
            push(type){
                var content = {content: this.current_content}
                switch (type) {
                    case 'end':
                        this.comments.push(content);
                        break;
                    case 'pre':
                        this.comments.unshift(content);
                        break;
                }
                this.current_content = '';
            },
            del(type){
                switch (type) {
                    case 'last':
                        this.comments.pop();
                        break;
                    case 'first':
                        this.comments.shift();
                        break;
                }
            }
        }
    });
</script>
</body>
</html>