javascript 常用函数

 1.格式化数值函数

function number_format (number, decimals, dec_point, thousands_sep) {
  // http://kevin.vanzonneveld.net
  // +   original by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +     bugfix by: Michael White (http://getsprink.com)
  // +     bugfix by: Benjamin Lupton
  // +     bugfix by: Allan Jensen (http://www.winternet.no)
  // +    revised by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // +     bugfix by: Howard Yeend
  // +    revised by: Luke Smith (http://lucassmith.name)
  // +     bugfix by: Diogo Resende
  // +     bugfix by: Rival
  // +      input by: Kheang Hok Chin (http://www.distantia.ca/)
  // +   improved by: davook
  // +   improved by: Brett Zamir (http://brett-zamir.me)
  // +      input by: Jay Klehr
  // +   improved by: Brett Zamir (http://brett-zamir.me)
  // +      input by: Amir Habibi (http://www.residence-mixte.com/)
  // +     bugfix by: Brett Zamir (http://brett-zamir.me)
  // +   improved by: Theriault
  // +      input by: Amirouche
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // *     example 1: number_format(1234.56);
  // *     returns 1: '1,235'
  // *     example 2: number_format(1234.56, 2, ',', ' ');
  // *     returns 2: '1 234,56'
  // *     example 3: number_format(1234.5678, 2, '.', '');
  // *     returns 3: '1234.57'
  // *     example 4: number_format(67, 2, ',', '.');
  // *     returns 4: '67,00'
  // *     example 5: number_format(1000);
  // *     returns 5: '1,000'
  // *     example 6: number_format(67.311, 2);
  // *     returns 6: '67.31'
  // *     example 7: number_format(1000.55, 1);
  // *     returns 7: '1,000.6'
  // *     example 8: number_format(67000, 5, ',', '.');
  // *     returns 8: '67.000,00000'
  // *     example 9: number_format(0.9, 0);
  // *     returns 9: '1'
  // *    example 10: number_format('1.20', 2);
  // *    returns 10: '1.20'
  // *    example 11: number_format('1.20', 4);
  // *    returns 11: '1.2000'
  // *    example 12: number_format('1.2000', 3);
  // *    returns 12: '1.200'
  // *    example 13: number_format('1 000,50', 2, '.', ' ');
  // *    returns 13: '100 050.00'
  // Strip all characters but numerical ones.
  number = (number + '').replace(/[^0-9+-Ee.]/g, '');
  var n = !isFinite(+number) ? 0 : +number,
    prec = !isFinite(+decimals) ? 0 : Math.abs(decimals),
    sep = (typeof thousands_sep === 'undefined') ? ',' : thousands_sep,
    dec = (typeof dec_point === 'undefined') ? '.' : dec_point,
    s = '',
    toFixedFix = function (n, prec) {
      var k = Math.pow(10, prec);
      return '' + Math.round(n * k) / k;
    };
  // Fix for IE parseFloat(0.55).toFixed(0) = 0;
  s = (prec ? toFixedFix(n, prec) : '' + Math.round(n)).split('.');
  if (s[0].length > 3) {
    s[0] = s[0].replace(/B(?=(?:d{3})+(?!d))/g, sep);
  }
  if ((s[1] || '').length < prec) {
    s[1] = s[1] || '';
    s[1] += new Array(prec - s[1].length + 1).join('0');
  }
  return s.join(dec);
}

 来源：http://phpjs.org/functions/number_format/

 2. 数值转换为科学计数法

       /*
　　　　 * number 传过来的值(保留两位小数)
        * 如果有其他要求，可做适当修改
       */    
　　　　function covertNumber(number)
       {
　　　　　　　var temp = number.split('.');
            var beforeLen = temp[0].length;
            if (beforeLen > 3)
            {
                if (temp[0].substr(3,1) > 4)
                {
                    var pointVal = temp[0].substr(1,1) + (parseInt(temp[0].substr(2,1))+1);
                } else {
                    var pointVal = temp[0].substr(1,2);
                }
            } else {
                var pointVal = temp[0].substr(1,2);
            }
            var powNumber = beforeLen-1 > 10 ? beforeLen-1 : '0'+beforeLen-1;
            
　　　　　　　return  temp[0].substr(0,1) + '.' + pointVal + 'E' + powNumber;

       }

 3. 窗口关闭事件

window.onbeforeunload   =   function(){   
      var   n   =   window.event.screenX   -   window.screenLeft;   
      var   b   =   n   >   document.documentElement.scrollWidth-20;   
      if(b   &&   window.event.clientY   <   0   ||   window.event.altKey)   
      {     
           if (confirm("要保存退出吗？"))
           {
                                            
            } else {
               
            }
      }
}