query或者JavaScript实现在textarea光标处插入文本

1.Jquery函数实现：

$(function() {
    /*  在textarea处插入文本--Start */
    (function($) {
        $.fn.extend({
                    insertContent : function(myValue, t) {
                        var $t = $(this)[0];
                        if (document.selection) { // ie
                            this.focus();
                            var sel = document.selection.createRange();
                            sel.text = myValue;
                            this.focus();
                            sel.moveStart('character', -l);
                            var wee = sel.text.length;
                            if (arguments.length == 2) {
                                var l = $t.value.length;
                                sel.moveEnd("character", wee + t);
                                t <= 0 ? sel.moveStart("character", wee - 2 * t
                                        - myValue.length) : sel.moveStart(
                                        "character", wee - t - myValue.length);
                                sel.select();
                            }
                        } else if ($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;
                            if (arguments.length == 2) {
                                $t.setSelectionRange(startPos - t,
                                        $t.selectionEnd + t);
                                this.focus();
                            }
                        } else {
                            this.value += myValue;
                            this.focus();
                        }
                    }
                })
    })(jQuery);
    /* 在textarea处插入文本--Ending */
});

调用方法：

$(文本域选择器).insertContent("插入的内容"); 
//$(文本域选择器).insertContent("插入的内容"，数值); //根据数值选中插入文本内容两边的边界, 数值: 0是表示插入文字全部选择，-1表示插入文字两边各少选中一个字符。

function insertText(obj,str) {
    if (document.selection) {
        var sel = document.selection.createRange();
        sel.text = str;
    } else if (typeof obj.selectionStart === 'number' && typeof obj.selectionEnd === 'number') {
        var startPos = obj.selectionStart,
            endPos = obj.selectionEnd,
            cursorPos = startPos,
            tmpStr = obj.value;
        obj.value = tmpStr.substring(0, startPos) + str + tmpStr.substring(endPos, tmpStr.length);
        cursorPos += str.length;
        obj.selectionStart = obj.selectionEnd = cursorPos;
    } else {
        obj.value += str;
    }
}
function moveEnd(obj){
    obj.focus();
    var len = obj.value.length;
    if (document.selection) {
        var sel = obj.createTextRange();
        sel.moveStart('character',len);
        sel.collapse();
        sel.select();
    } else if (typeof obj.selectionStart == 'number' && typeof obj.selectionEnd == 'number') {
        obj.selectionStart = obj.selectionEnd = len;
    }
}