Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource


Babel is required to process package imports. If you need a different preprocessor remove all packages first.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.


              <div id="app">
  <button @click="add">修改对象的count属性触发watch</button>
  <button @click="addPrototype">修改对象的a属性触发watch</button>




              const vm = new Vue({
  el: "#app",
  data: {
    obj: {
      count: 0,
      a: "默认",
        a: 1
    step: 1
  created:()=>{ // 箭头函数问题 this指向undefined
  watch: {
      handler(val, oldVal){
        console.log("啦啦啦", this.obj, val, oldVal);
      deep: true,
      immediate: true
    step: {
      handler(val, oldVal) {
        console.log("默认触发一次", val, oldVal);
      immediate: true
  methods: {
    add() {
      this.obj.count = this.obj.count + this.step;
      this.step += 1;
    addPrototype() {
      this.obj.c.a++; // 支持多层属性监听
      // this.obj.a = this.obj.count; 
      // this.obj.c= this.obj.count;
      //  如果把上面第一行注释,第二行取消注释
      // 那么将不会触发深度watch因为自己添加的属性里面没有get set方法 c属性不会被监听