<zk-button class="btn btn-default">默认按钮</zk-button>
<zk-button class="btn btn-default btn-round">默认按钮</zk-button>
<zk-button class="btn btn-default btn-round" :speed="4" :opacity="0.6">定义速度和初始的波浪透明度</zk-button>

<template>
 <button class="zk-btn">
  <canvas class="zk-ripple" @click="ripple"></canvas>
  <slot></slot>
 </button>
</template>

ripple(event) {
 // 清除上次没有执行的动画
 if (this.timer) {
  window.cancelAnimationFrame(this.timer);
 }
 this.el = event.target;
 // 执行初始化
 if (!this.initialized) {
  this.initialized = true;
  this.init(this.el);
 }
 this.radius = 0;
 // 点击坐标原点
 this.origin.x = event.offsetX;
 this.origin.y = event.offsetY;
 this.context.clearRect(0, 0, this.el.width, this.el.height);
 this.el.style.opacity = this.opacity;
 this.draw();
},

draw() {
 this.context.beginPath();
 // 绘制波纹
 this.context.arc(this.origin.x, this.origin.y, this.radius, 0, 2 * Math.PI, false);
 this.context.fillStyle = this.color;
 this.context.fill();
 // 定义下次的绘制半径和透明度
 this.radius += this.speed;
 this.el.style.opacity -= this.speedOpacity;
 // 通过判断半径小于元素宽度或者还有透明度，不断绘制圆形
 if (this.radius < this.el.width || this.el.style.opacity > 0) {
  this.timer = window.requestAnimationFrame(this.draw);
 } else {
  // 清除画布
  this.context.clearRect(0, 0, this.el.width, this.el.height);
  this.el.style.opacity = 0;
 }
}