将文本框设置成带有千位分隔符的财务专用数字输入框

　扩展方法，设置文本框：

/*

 * @param {Reg} reg 用来限制输入字符的格式，如位数，长度，取值范围等
 */

 1　$.fn.TextBoxThousandNumInput = function (reg) {
        var obj = $(this);
        var oldvalue = obj.val();
        var cursorPos = "";
        obj.keyup(function () {
            var newvalue = obj.val();
            cursorPos = obj.getCursorPosition();
            if (newvalue == "") return obj;
            newvalue = toNormalNum(newvalue);
            if (!newvalue.match(reg)) {
                obj.val(toThousands(oldvalue));
            } else {
                obj.val(toThousands(newvalue));
            }
            var offset=toThousands(newvalue).length-toThousands(oldvalue).length;
            if ( offset < -1) {
                setCursorPosition(this, cursorPos-1);
            } else if (offset > 0) {
                setCursorPosition(this, cursorPos+offset - 1);
            } else {
                setCursorPosition(this, cursorPos);
            }
            oldvalue =toNormalNum( obj.val());
        });
        return obj;
    }

调用：

$(selector).TextBoxThousandNumInput (reg);

　将数字转换为带有千位分隔符的数字：

var toThousands = function (num) {
    var num = (num || '').toString(), re = /(d{3}|d{3}.d{0,2})$/, result = '';
    while (re.test(num)) {
        result = RegExp.lastMatch + result;
        if (num !== RegExp.lastMatch) {
            result = ',' + result;
            num = RegExp.leftContext;
        } else {
            num = '';
            break;
        }
    }
    if (num) { result = num + result; }
    return result;
}

　将千位分割数字转换为普通数字：

var toNormalNum = function (numStr) {
    return numStr.replace(/\,/g, '');
}

　设置文本区域光标位置：

   /*
 * @param {HTMLInputElement/HTMLTextAreaElement} elem
 * @param {Number} index
 */
    var setCursorPosition= function (elem, index) {
        var val = elem.value
        var len = val.length

        // 超过文本长度直接返回
        if (len < index) return
        (function () {
            elem.focus()
            if (elem.setSelectionRange) { // 标准浏览器
                elem.setSelectionRange(index, index)
            } else { // IE9-
                var range = elem.createTextRange()
                range.moveStart("character", -len)
                range.moveEnd("character", -len)
                range.moveStart("character", index)
                range.moveEnd("character", 0)
                range.select()
            }
        })();
    }

  获取输入框光标定位：

$.fn.getCursorPosition = function () {
        var el = $(this).get(0);
        var pos = 0;
        if ('selectionStart' in el) {
            pos = el.selectionStart;
        } else if ('selection' in document) {
            el.focus();
            var Sel = document.selection.createRange();
            var SelLength = document.selection.createRange().text.length;
            Sel.moveStart('character', -el.value.length);
            pos = Sel.text.length - SelLength;
        }
        return pos;
    }