Vue 实现展开折叠效果

效果参见：https://segmentfault.com/q/1010000011359250/a-1020000011360185

上述链接中，大佬给除了解决方法，再次进行总结，方便以后使用。

除了使用jQuery的方式实现上述效果，同样可以在Vue实现，下面是解决办法：

1、创建collapse.js文件

const elTransition =
  "0.3s height ease-in-out, 0.3s padding-top ease-in-out, 0.3s padding-bottom ease-in-out";
const Transition = {
  "before-enter"(el) {
    el.style.transition = elTransition;
    if (!el.dataset) el.dataset = {};

    el.dataset.oldPaddingTop = el.style.paddingTop;
    el.dataset.oldPaddingBottom = el.style.paddingBottom;

    el.style.height = 0;
    el.style.paddingTop = 0;
    el.style.paddingBottom = 0;
  },

  enter(el) {
    el.dataset.oldOverflow = el.style.overflow;
    if (el.scrollHeight !== 0) {
      el.style.height = el.scrollHeight + "px";
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    } else {
      el.style.height = "";
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    }

    el.style.overflow = "hidden";
  },

  "after-enter"(el) {
    el.style.transition = "";
    el.style.height = "";
    el.style.overflow = el.dataset.oldOverflow;
  },

  "before-leave"(el) {
    if (!el.dataset) el.dataset = {};
    el.dataset.oldPaddingTop = el.style.paddingTop;
    el.dataset.oldPaddingBottom = el.style.paddingBottom;
    el.dataset.oldOverflow = el.style.overflow;

    el.style.height = el.scrollHeight + "px";
    el.style.overflow = "hidden";
  },

  leave(el) {
    if (el.scrollHeight !== 0) {
      el.style.transition = elTransition;
      el.style.height = 0;
      el.style.paddingTop = 0;
      el.style.paddingBottom = 0;
    }
  },

  "after-leave"(el) {
    el.style.transition = "";
    el.style.height = "";
    el.style.overflow = el.dataset.oldOverflow;
    el.style.paddingTop = el.dataset.oldPaddingTop;
    el.style.paddingBottom = el.dataset.oldPaddingBottom;
  }
};

export default {
  name: "collapseTransition",
  functional: true,
  render(h, { children }) {
    const data = {
      on: Transition
    };
    return h("transition", data, children);
  }
};

2、在.vue组件中引入