add lib folder

lib/util/index.js

@@ -0,0 +1,39 @@
+export function randomExtend (minNum, maxNum) {
+  if (arguments.length === 1) {
+    return parseInt(Math.random() * minNum + 1, 10)
+  } else {
+    return parseInt(Math.random() * (maxNum - minNum + 1) + minNum, 10)
+  }
+}
+
+export function debounce (delay, callback) {
+  let lastTime
+
+  return function () {
+    clearTimeout(lastTime)
+
+    const [that, args] = [this, arguments]
+
+    lastTime = setTimeout(() => {
+      callback.apply(that, args)
+    }, delay)
+  }
+}
+
+export function observerDomResize (dom, callback) {
+  const MutationObserver = window.MutationObserver || window.WebKitMutationObserver || window.MozMutationObserver
+
+  const observer = new MutationObserver(callback)
+
+  observer.observe(dom, { attributes: true, attributeFilter: ['style'], attributeOldValue: true })
+
+  return observer
+}
+
+export function getPointDistance (pointOne, pointTwo) {
+  const minusX = Math.abs(pointOne[0] - pointTwo[0])
+
+  const minusY = Math.abs(pointOne[1] - pointTwo[1])
+
+  return Math.sqrt(minusX * minusX + minusY * minusY)
+}