实用jquery扩展收集（1）：在光标处插入内容 和 获取textarea选中的值

$.fn.extend({
insertAtCursor : function(myValue) {
var $t = $(this)[0];
if (document.selection) {
this.focus();
sel = document.selection.createRange();
sel.text = myValue;
this.focus();
} else if ($t.selectionStart || $t.selectionStart == '0') {
var startPos = $t.selectionStart;
var endPos = $t.selectionEnd;
var scrollTop = $t.scrollTop;
$t.value = $t.value.substring(0, startPos) + myValue + $t.value.substring(endPos, $t.value.length);
this.focus();
$t.selectionStart = startPos + myValue.length;
$t.selectionEnd = startPos + myValue.length;
$t.scrollTop = scrollTop;
} else {
this.value += myValue;
this.focus();
}
}
});

$.fn.selection = function(){
var s,e,range,stored_range;
if(this[0].selectionStart == undefined){
var selection=document.selection;
if (this[0].tagName.toLowerCase() != "textarea") {
var val = this.val();
range = selection.createRange().duplicate();
range.moveEnd("character", val.length);
s = (range.text == "" ? val.length:val.lastIndexOf(range.text));
range = selection.createRange().duplicate();
range.moveStart("character", -val.length);
e = range.text.length;
}else {
range = selection.createRange(),
stored_range = range.duplicate();
stored_range.moveToElementText(this[0]);
stored_range.setEndPoint('EndToEnd', range);
s = stored_range.text.length - range.text.length;
e = s + range.text.length;
}
}else{
s=this[0].selectionStart,
e=this[0].selectionEnd;
}
var te=this[0].value.substring(s,e);
return {start:s,end:e,text:te};
};