/*

 *   功能:实现VBScript的DateAdd功能.

 *   参数:interval,字符串表达式，表示要添加的时间间隔.

 *   参数:number,数值表达式，表示要添加的时间间隔的个数.

 *   参数:date,时间对象.

 *   返回:新的时间对象.

 *   var now = new Date();

 *   var newDate = DateAdd( "d", 5, now);

 *---------------   DateAdd(interval,number,date)   -----------------

 */

function DateAdd(interval, number, date) {

    switch (interval) {

    case "y ": {

        date.setFullYear(date.getFullYear() + number);

        return date;

        break;

    }

    case "q ": {

        date.setMonth(date.getMonth() + number * 3);

        return date;

        break;

    }

    case "m ": {

        date.setMonth(date.getMonth() + number);

        return date;

        break;

    }

    case "w ": {

        date.setDate(date.getDate() + number * 7);

        return date;

        break;

    }

    case "d ": {

        date.setDate(date.getDate() + number);

        return date;

        break;

    }

    case "h ": {

        date.setHours(date.getHours() + number);

        return date;

        break;

    }

    case "m ": {

        date.setMinutes(date.getMinutes() + number);

        return date;

        break;

    }

    case "s ": {

        date.setSeconds(date.getSeconds() + number);

        return date;

        break;

    }

    default: {

        date.setDate(d.getDate() + number);

        return date;

        break;

    }

    }

}

var now = new Date();

// 加五天.

var newDate = DateAdd("d ", 5, now);

alert(newDate.toLocaleDateString())

// 加两个月.

newDate = DateAdd("m ", 2, now);

alert(newDate.toLocaleDateString())

// 加一年

newDate = DateAdd("y ", 1, now);

alert(newDate.toLocaleDateString())