JS实现在文本指定位置插入内容的简单示例

实例如下所示：

function insertAtCursor(myField, myValue) {

//IE 浏览器
if (document.selection) {
 myField.focus();
 sel = document.selection.createRange();
 sel.text = myValue;
 sel.select();
}

//FireFox、Chrome等
else if (myField.selectionStart || myField.selectionStart == '0') {
 var startPos = myField.selectionStart;
 var endPos = myField.selectionEnd;

// 保存滚动条
 var restoreTop = myField.scrollTop;
 myField.value = myField.value.substring(0, startPos) + myValue + myField.value.substring(endPos, myField.value.length);

if (restoreTop > 0) {
 myField.scrollTop = restoreTop;
 }

myField.focus();
 myField.selectionStart = startPos + myValue.length;
 myField.selectionEnd = startPos + myValue.length;
} else {
 myField.value += myValue;
 myField.focus();
}
}
<textarea id="textarea" style="width: 386px; height: 260px">
</textarea>
<input type="text" id="text" />
<input type="button" value="插入" onclick="insertAtCursor(document.getElementById('textarea'),document.getElementById('text').value)" />

来源：http://blog.csdn.net/qq_20960159/article/details/78820023