haslayout是IE7-浏览器的特有属性。hasLayout是一种只读属性，有两种状态:true或false。当其为true时，代表该元素有自己的布局，否则代表该元素的布局继承于父元素。
[注意]通过element.currentStyle.hasLayout可以得出当前元素的hasLayout情况
【1】html,body
【2】table,tr,th,td
【3】img
【4】hr
【5】input,button,select,textarea,fieldset
【6】frameset,frame,iframe
【1】display:inline-blcok
【2】height/width:除了auto
【3】float:left/right
【4】position:absolute
【5】writing-mode(IE专有属性，设置文本的垂直显示):tb-rl
【6】zoom(IE专有属性，设置或检索对象的缩放比例):除了normal
【IE7专有的触发hasLayout的CSS属性】
【1】min-height/max-height/min-width/max-width:除none
【2】overflow\overflow-x\overflow-y:除visible
【3】position:fixed
【1】解决IE7-浏览器下父级边框不阻止子级上下margin传递的bug
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><style>body{ margin: 0;}ul{ margin: 0; padding: 0; list-style: none;}.list{ border: 10px solid black; background-color: red; /*触发hasLayout*/ /*float:left;*/}.in{ height: 100px; width: 100px; margin-top: 50px; background-color: blue;}</style></head><body><ul class="list"> <li class="in"></li></ul></body> </html>
【2】配合display:inline让块元素模拟inline-block
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><style>body{ margin: 0;}.box{ width: 100px; height: 100px; background-color: red; display:inline-block; /*配合display:inline触发hasLayout*/ /* float:left; display:inline; */}</style></head><body><div class="box" id="box"></div><span>测试inline-block用</span></body> </html>
【3】解决在IE7-浏览器下LI4px空隙bug(IE7-浏览器下li有高度或宽度或zoom:1，且仅包含内联元素，且内联元素被设置为display:block，li下会多出3px的垂直间距)
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><style>body{ margin: 0;}ul{ margin: 0; padding: 0; list-style: none;}.list{ width: 200px; background-color: lightgreen;}.in{ height: 100px; background-color: lightblue;}.span{ display: block; zoom:1;}</style></head><body><ul class="list"> <li class="in"> <span class="span">1231</span> </li> <li class="in"> <span class="span">1232</span> </li></ul></body> </html>
【4】触发浮动元素的父级的hasLayout，浮动元素会被layout元素自动包含，相当于IE7-浏览器下实现清浮动
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><style>body{ margin: 0;}ul{ margin: 0; padding: 0; list-style: none;}.list{ background-color: lightgreen; height: 200px;}.in{ float: left; width: 100px; height: 100px; border: 1px solid black; background-color: lightblue;}.test{ width: 100px; height: 150px; background-color: yellow;}</style></head><body><ul class="list"> <li class="in"></li> <li class="in"></li></ul><div class="test">测试浮动</div></body> </html>
