在光标处插入字符串的实现代码 兼容IE,Firefox

// 在光标处插入字符串
// myField 文本框对象
// 要插入的值
function insertAtCursor(myField, myValue)
{
//IE support
if (document.selection)
{
myField.focus();
sel = document.selection.createRange();
sel.text = myValue;
sel.select();
}
//MOZILLA/NETSCAPE support
else if (myField.selectionStart || myField.selectionStart == '0')
{
var startPos = myField.selectionStart;
var endPos = myField.selectionEnd;
// save scrollTop before insert
var restoreTop = myField.scrollTop;
myField.value = myField.value.substring(0, startPos) + myValue + myField.value.substring(endPos,myField.value.length);
if (restoreTop > 0)
{
// restore previous scrollTop
myField.scrollTop = restoreTop;
}
myField.focus();
myField.selectionStart = startPos + myValue.length;
myField.selectionEnd = startPos + myValue.length;
} else {
myField.value += myValue;
myField.focus();
}
}