What are the js functions that retain two decimal places?

js functions that retain two decimal places include: 1. [toFixed()] function; 2. [Math.floor()] function does not round, but rounds down; 3. Use string matching method; 4. Round to 2 decimal places; 5. Float to 2 decimal places.

js functions that retain two decimal places are:

1. Rounding related

1. toFixed() method

Please note that two decimal places are retained and the numerical type data is changed into a string type

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

2. Math.floor() , do not round, round down

Note, do not change the data type

// 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. String matching

Note, first convert the data into a string, and finally Convert to numeric type

// 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. Round and keep 2 decimal places (if the second decimal place is 0, keep one decimal place)

Note that the data type remains unchanged

//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. Round to keep 2 decimal places (if there are not enough digits, use 0 as substitute)

Note that the data type changes to string type

//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 += &#39;.&#39;;
             }
             // 当数字的长度< 小数点索引+2时，补0
             while (s_x.length <= pos_decimal + 2) {
                 s_x += &#39;0&#39;;
             }
             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

2. Keep two decimal places for floating point numbers decimal places

1. Round the floating point number to 2 decimal places

Note that the data type remains unchanged

//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. Force 2 decimal places to be retained. For example: 2, 00 will be added after 2. That is, 2.00

Note that the data type changes to string type

//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 += &#39;.&#39;;
           }
           while (s.length <= rs + 2) {
            s += &#39;0&#39;;
           }
           return s;
          }
          console.log(toDecimal2(3.1)); // 3.10
          console.log(typeof toDecimal2(3.1415926)); //string

3. Keep two decimal places and the floating point number will not be filled if there are not enough rounding digits. 0

Note that the data type remains unchanged

// 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)); //numbe

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