js金额价格四舍五入保留2位小数demo效果（整理）

四舍五入保留2位小数（不够位数，则用0替补）
function keepTwoDecimalFull(num) {
    
    
     var result = parseFloat(num);
     if (isNaN(result)) {
    
    
         alert('传递参数错误，请检查！');
         return false;
     }
     result = Math.round(num * 100) / 100;
     var s_x = result.toString(); //将数字转换为字符串

     var pos_decimal = s_x.indexOf('.'); //小数点的索引值


     // 当整数时，pos_decimal=-1 自动补0
     if (pos_decimal < 0) {
    
    
         pos_decimal = s_x.length;
         s_x += '.';
     }

     // 当数字的长度< 小数点索引+2时，补0
     while (s_x.length <= pos_decimal + 2) {
    
    
         s_x += '0';
     }
     return s_x;
}

 console.log(keepTwoDecimalFull(120.5)); //120.50
 console.log(typeof keepTwoDecimalFull(120.5)); //string
 console.log(keepTwoDecimalFull(2.446242342)); //2.45
 console.log(typeof keepTwoDecimalFull(2.446242342)); //string

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