[JSP] js保留两位小数方法总结

// 1.四舍五入
var num =2.446242342;  
num = num.toFixed(2); 
console.log(num); //2.45
console.log(typeof num); // string

// 2.不四舍五入 向下取整
num = Math.floor(num * 100) / 100;
console.log(num); //2.44
console.log(typeof num); // number

// 3.不四舍五入 字符串匹配再转换
num = Number(num.toString().match(/^\d+(?:\.\d{0,2})?/));
console.log(num); //2.44
console.log(typeof num); // number

//4.四舍五入保留2位小数（若第二位小数为0，则保留一位小数）
function keepTwoDecimal(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;
    return result;
};
keepTwoDecimal(num);
console.log(num); //2.44
console.log(typeof num); //number

//5.四舍五入保留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

//浮点数保留两位小数
//1.功能：将浮点数四舍五入，取小数点后2位
function toDecimal(x) {
var f = parseFloat(x);
if (isNaN(f)) {
return;
}
f = Math.round(x*100)/100;
return f;
}
console.log(toDecimal(3.1465926)); // 3.15
console.log(typeof toDecimal(3.1415926)); //number

//2.强制保留2位小数，如：2，会在2后面补上00.即2.00
function toDecimal2(x) {
var f = parseFloat(x);
if (isNaN(f)) {
  return false;
}
var f = Math.round(x*100)/100;
var s = f.toString();
var rs = s.indexOf('.');
if (rs < 0) {
  rs = s.length;
  s += '.';
}
while (s.length <= rs + 2) {
  s += '0';
}
return s;
}
console.log(toDecimal2(3.1)); // 3.10
console.log(typeof toDecimal2(3.1415926)); //string

// 3.保留两位小数 浮点数四舍五入 位数不够 不补0
function fomatFloat(src,pos){
  return Math.round(src*Math.pow(10, pos))/Math.pow(10, pos);
  }
console.log(fomatFloat(3.12645,2)); // 3.13
console.log(typeof fomatFloat(3.1415926)); //number