vue custom instructions implement v-tap plug-in

vue-touch is based on hammer, which is too large for ordinary simple gesture pages!

So I wanted to implement one of the most commonly used gesture taps myself. Following the custom instructions and plug-in documentation, I implemented a v-tap instruction last night and posted this article.

Instructions and plug-ins introduction
Custom instructions and plug-ins are also introduced in the official documentation in a relatively simple and detailed manner, so I won’t go into too much detail.
Let me start by saying that this plug-in uses three APIs. If you don’t understand them, it’s best to read the documentation in advance to avoid confusion in the subsequent code.

Instruction part
1.update(nVal,oVal)
2.acceptStatement

Plug-in part
Vue.use()

Then we need to learn the format of writing Vue plug-ins like writing jQuery plug-ins.

Continue to the official document

MyPlugin.install = function (Vue, options) {
 // 1. 添加全局方法或属性
 Vue.myGlobalMethod = ...
 // 2. 添加全局资源
 Vue.directive('my-directive', {})
 // 3. 添加实例方法
 Vue.prototype.$myMethod = ...
}

Don’t you still understand? Then we can look directly at the author's plug-in code.

;(function () {
 
 var vueTouch = {}
 
 vueTouch.install = function (Vue) {
 
 Vue.directive('touch', {
 
  isFn: true,
  acceptStatement: true,
 
  bind: function () {
 
  },
 
  update: function (fn) {
 
  },
 
  unbind: function () {
 
  }
 })
 }
 
 if (typeof exports == "object") {
 module.exports = vueTouch
 } else if (typeof define == "function" && define.amd) {
 define([], function(){ return vueTouch })
 } else if (window.Vue) {
 window.VueTouch = vueTouch
 Vue.use(vueTouch)
 }
 
})()

I deleted all the redundant irrelevant code, and you can find that the format is actually like this, and the rest can be written directly using our own js skills.
PS: Regarding the attribute "isFn:true", I did not find relevant information in the document. I personally think it may be a comment, indicating that this instruction requires an expression of fn (this is the expression of the instruction, see the instruction instance attribute for details) .

Just do it

First, write the outer layer according to the plug-in format.

;(function() {
 var vueTap = {};
 vueTap.install = function(Vue) {
 
 };
 
 if (typeof exports == "object") {
  module.exports = vueTap;
 } else if (typeof define == "function" && define.amd) {
  define([], function(){ return vueTap })
 } else if (window.Vue) {
  window.vueTap = vueTap;
  Vue.use(vueTap);
 }
 
})();

Then write our own custom instructions in our vueTap.install

Vue.directive('tap', {
  isFn : true,
  bind : function() {
 
  },
  update : function(fn) {
 
  },
  unbind : function() {},
  isTap : function() {
   //判断是否为tap
  },
  touchstart : function(e,self) {
 
  },
  touchend : function(e,self) {
 
  }
 });
};

Since only update has parameters to pass and can receive our expression, so I bound the event The processing procedures are all written in the update.

PS: Of course, some friends like to assign all fn to this (here this is a directve instance), and finally bind the event at the bind location. I haven't found the standard for this, and I don't know which one is better to write.

update : function(fn) {
 var self = this; //存下this，方便以后用
  //在directive上绑定的属性和方法
  //都可通过self.xxx self.touchstart()获取
  self.tapObj = {}; //初始化我们的tap对象
 
 if(typeof fn !== 'function') {
 //你别给我搞事！
  return console.error('The param of directive "v-tap" must be a function!');
 }
 
 self.handler = function(e) { //给当前directive存个handler方便之后调用
  e.tapObj = self.tapObj;
  //把我们的tap对象赋值给原生event对象上，方便回调里获取参数
  fn.call(self,e);
 };
 
 //把我们的start和end剥离出来，写在directive上
 //由于只有tap事件，所以我们在move过程就不需要做处理
 this.el.addEventListener('touchstart',function(e) {
  self.touchstart(e,self);
 },false);
 
 this.el.addEventListener('touchend',function(e) {
  self.touchend(e,self,fn);
 },false);
 
}

In update, it is very simple, which is the process of initialization, event binding and assigning values ​​to instances.
The last step is the logical processing of isTap, touchstart, and touchend.

isTap : function() {
 var tapObj = this.tapObj;
 return this.time < 150 && Math.abs(tapObj.distanceX) < 2 && Math.abs(tapObj.distanceY) < 2;
},
touchstart : function(e,self) {
 var touches = e.touches[0];
 var tapObj = self.tapObj;
 tapObj.pageX = touches.pageX;
 tapObj.pageY = touches.pageY;
 tapObj.clientX = touches.clientX;
 tapObj.clientY = touches.clientY;
 self.time = +new Date();
},
touchend : function(e,self) {
 var touches = e.changedTouches[0];
 var tapObj = self.tapObj;
 self.time = +new Date() - self.time;
 tapObj.distanceX = tapObj.pageX - touches.pageX;
 tapObj.distanceY = tapObj.pageY - touches.pageY;
 
 if (self.isTap(tapObj))
  self.handler(e);
}

Finally there is a big question, how can we make our expression accept parameters?

<ul>
 <li v-for="el in list"
  v-tap="args($index,el,$event)"
   >
  {{el.name}}---{{el.age}}
 </li>
</ul>

Then we need to add an attribute acceptStatement:true to our directive (see the document acceptStatement for details)

Summary
Written this v-tap plug-in to share with you some experiences.
1. This in update points to the directive instance, not vm, nor dom
2. Customizable properties and methods can be used in the directive('name',{}) object. The call is self.xxx
3. Enable custom instructions to accept inline statements acceptStatement:true
4. Don’t forget Vue.use(obj) for the final interface
I don’t have v-tap.stop, v-tap.prevent here , v-tap.stop.prevent is used for processing, you can implement it yourself! Also very simple.