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

(1):在光标处插入值

$.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();
            }
        }
    });

(2):获取textarea选中的值

$.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};
    };