2014年7月18日 星期五

[JS] html select 下拉框 顯示固定寬度

預設的 select box 的寬度會依照 option 裡的值(value) 長短而自動 resize 寬度, 在很多 select box 的畫面裡會不太好太, 解法有2:

  • 1. css (建議), min-width & max-width 屬性.
  • 2. javascript.

解法1:

Example

Set the minimum width of a paragraph:
p{
min-width:1000px;
}

Browser Support: ALL Browser


The min-width property is supported in all major browsers.
Note: IE6 and earlier versions do not support the min-width property.

html code:
<select name="Select1" style="min-width:100px; max-width:120px;">

執行畫面 (screent shot):


解法2: javascritp

執行畫面:


javascript source code:
==============
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<script type="text/javascript">
function FixWidth(selectObj)
{
    var newSelectObj = document.createElement("select");
    newSelectObj = selectObj.cloneNode(true);
    newSelectObj.selectedIndex = selectObj.selectedIndex;
    newSelectObj.onmouseover = null;
    var e = selectObj;
    var absTop = e.offsetTop;
    var absLeft = e.offsetLeft;
    while(e = e.offsetParent)
    {
        absTop += e.offsetTop;
        absLeft += e.offsetLeft;
    }
    with (newSelectObj.style)
    {
        position = "absolute";
        top = absTop + "px";
        left = absLeft + "px";
        width = "auto";
    }
    var rollback = function(){ RollbackWidth(selectObj, newSelectObj); };
    if(window.addEventListener)
    {
        newSelectObj.addEventListener("blur", rollback, false);
        newSelectObj.addEventListener("change", rollback, false);
    }
    else
    {
        newSelectObj.attachEvent("onblur", rollback);
        newSelectObj.attachEvent("onchange", rollback);
    }
    selectObj.style.visibility = "hidden";
    document.body.appendChild(newSelectObj);
    newSelectObj.focus();
}
function RollbackWidth(selectObj, newSelectObj)
{
    selectObj.selectedIndex = newSelectObj.selectedIndex;
    selectObj.style.visibility = "visible";
    document.body.removeChild(newSelectObj);
}
</script>
</head>
<body>
<form method="post">
    <div style="width:100px; height:100px; margin:100px; padding:10px; background:gray;">
        <select name="Select1" style="width:80px;" onmouseover="FixWidth(this)">
            <option id="A" title="this is A">AAAAAAAAAAAAAAA</option>
            <option id="B" title="this is B">BBBBBBBBBBBBBBB</option>
            <option id="C" title="this is C">CCCCCCCCCCCCCCC</option>
        </select>
    </div>
</form>
</body>
</html>

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