在制作富文本编辑器，尤其是在制作以div元素为编辑器区域时，当鼠标离开编辑区域以后会失去焦点，失去选区，这时候就要通过selection&range来重新设置选区。【以下代码尚未考虑IE低版本，请在现代浏览器下测试学习】
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>range</title>
<style type="text/css">
#edit{
100%;
height: 300px;
border: 1px solid #ccc;
}
</style>
</head>
<body>
<div contenteditable="true" id="edit">
<p>通过一个富文本编辑器，学习JavaScript！</p>
</div>
<div id="button">button</div>
<script type="text/javascript">
var edit = document.getElementById('edit');
var button = document.getElementById('button');
edit.addEventListener('mouseup', function() {
saveSelection();
});
button.addEventListener('click', function() {
restoreSelection();
document.execCommand('underline', false, null);
saveSelection();
});
function saveSelection() {
selection = document.getSelection();
save = selection.getRangeAt(0);
}
function restoreSelection() {
var selection = window.getSelection();
if(selection.rangeCount > 0) {
selection.removeAllRanges();
}
var range = document.createRange();
selection.addRange(save);
}
</script>
</body>
</html>