document.addEventListener('DOMContentLoaded', function() {//动态创建回到首页domvar backDom = document.createElement("div");backDom.className = "z-back";backDom.innerHTML = '<a href="/"><svg class="icon-back" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg"><path fill="#ffffff" d="M879.461 517.238l-366.588-336.911-368.334 335.167c-6.983 6.983-6.983 17.457 0 24.441s17.457 6.983 24.441 0l343.894-314.219 343.894 314.219c3.492 3.492 6.983 5.238 12.219 5.238s8.726-1.745 12.219-5.238c5.238-5.238 5.238-15.712-1.745-22.695zM767.739 524.219c-10.474 0-17.457 6.983-17.457 17.457v267.084h-143.143v-186.784h-190.277v186.784h-143.143v-267.084c0-10.474-8.726-17.457-17.457-17.457-10.474 0-17.457 6.983-17.457 17.457v301.997h214.715v-186.784h118.704v186.784h214.715v-301.997c-1.745-10.474-8.726-17.457-19.202-17.457zM642.051 274.591h106.484v92.519c0 10.474 8.726 17.457 17.457 17.457 10.474 0 17.457-6.983 17.457-17.457v-127.433h-143.143c-10.474 0-17.457 6.983-17.457 17.457 1.745 8.726 10.474 17.457 19.202 17.457z"  /></svg></a>';document.body.appendChild(backDom);//回到首页拖拽效果//获取屏幕宽高var screenW = window.screen.availWidth;var screenH = window.screen.availHeight;var dragBox = document.querySelector(".z-back");dragBox.addEventListener("touchstart", function(e) {var touch = e.touches[0];startX = touch.pageX;startY = touch.pageY;var left = getCss(dragBox, "left");var top = getCss(dragBox, "top");var width = getCss(dragBox, "width");var height = getCss(dragBox, "height");dragBox.addEventListener("touchmove", function(e) {e.preventDefault();var touch = e.touches[0];var x = touch.pageX - startX;var y = touch.pageY - startY;var nowLeft = left + x;var nowTop = top + y;//边界值处理if(x > 0){nowLeft = nowLeft > screenW - width ? screenW - width : nowLeft;}else{nowLeft = nowLeft > 0 ? nowLeft : 0;}if(y > 0){nowTop = nowTop > screenH - height ? screenH - height : nowTop;}else{nowTop = nowTop > 0 ? nowTop : 0;}dragBox.style.left = nowLeft + "px";dragBox.style.top = nowTop + "px";}, false);}, false);dragBox.addEventListener("touchend", function(e) {dragBox.removeEventListener("touchstart,touchmove,touchend", function() {});}, false)
}, false);//获取元素样式
function getCss(curEle, attr) {var val = null,reg = null;if ("getComputedStyle" in window) {val = window.getComputedStyle(curEle, null)[attr];} else {if (attr === "opacity") {val = curEle.currentStyle["filter"];reg = /^alpha\(opacity=(\d+(?:\.\d+)?)\)$/i;val = reg.test(val) ? reg.exec(val)[1] / 100 : 1;} else {val = curEle.currentStyle[attr];}}reg = /^(-?\d+(\.\d+)?)(px|pt|rem|em)?$/i;return reg.test(val) ? parseFloat(val) : val;
}