Js to float two decimal places

(link: https://www.jb51.net/article/154898.htm)

(link: https://www.jb51.net/article/154898.htm)

Here's how to implement JavaScript with two decimal places:
rounded
The following results will be rounded:

var num =2.446242342;
num = num.toFixed(2); //  The output result is  2.45

No rounding
The following processing results will not be rounded:
First, round off the decimal:

Math.floor(15.7784514000 * 100) / 100 
//  The output result is  15.77

The second, as a string, USES regular matching:

Number(15.7784514000.toString().match(/^d+(?:.d{0,2})?/)) 
//  The output result is  15.77, Cannot be used for integers such as  10  You must write to 10.0000

Note: if it is a negative number, convert it to a positive number and then calculate it

Javascript keeps instances of two decimal places:

<script type="text/javascript"> 
 //Keep two decimal places
 //Function: round floating point number to 2 decimal places
 function toDecimal(x) { 
  var f = parseFloat(x); 
  if (isNaN(f)) { 
  return; 
  } 
  f = Math.round(x*100)/100; 
  return f; 
 } 
 
 
 //The system retains two decimal places, such as: 2, which is followed by 00. That is, 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; 
 } 
  
 function fomatFloat(src,pos){ 
  return Math.round(src*Math.pow(10, pos))/Math.pow(10, pos); 
 } 
 //rounded
 alert(" keep 2 Decimal places: " + toDecimal(3.14159267)); 
 alert(" Mandatory reserves 2 Decimal places: " + toDecimal2(3.14159267)); 
 alert(" keep 2 Decimal places: " + toDecimal(3.14559267)); 
 alert(" Mandatory reserves 2 Decimal places: " + toDecimal2(3.15159267)); 
 alert(" keep 2 Decimal places: " + fomatFloat(3.14559267, 2)); 
 alert(" keep 1 Decimal places: " + fomatFloat(3.15159267, 1)); 
  
 //Six into five shekels
 alert(" keep 2 Decimal places: " + 1000.003.toFixed(2)); 
 alert(" keep 1 Decimal places: " + 1000.08.toFixed(1)); 
 alert(" keep 1 Decimal places: " + 1000.04.toFixed(1)); 
 alert(" keep 1 Decimal places: " + 1000.05.toFixed(1)); 
  
 //Scientific count
 alert(3.1415.toExponential(2)); 
 alert(3.1455.toExponential(2)); 
 alert(3.1445.toExponential(2)); 
 alert(3.1465.toExponential(2)); 
 alert(3.1665.toExponential(1)); 
 //To n bits, no n bits
 alert(" Accurate to the decimal point 2 position " + 3.1415.toPrecision(2)); 
 alert(" Accurate to the decimal point 3 position " + 3.1465.toPrecision(3)); 
 alert(" Accurate to the decimal point 2 position " + 3.1415.toPrecision(2)); 
 alert(" Accurate to the decimal point 2 position " + 3.1455.toPrecision(2)); 
 alert(" Accurate to the decimal point 5 position " + 3.141592679287.toPrecision(5)); 
 </script> 

Using Javascript to get a float to two decimal places, for example 22.127456 to 22.13, how to do?

1. Discard the decimals and keep the integers

ParseInt (5/2)

2. Round up, add 1 to the whole number if there are decimals

Math. Ceil (5/2)

3. Round.

Math. Round (5/2)

4, round down

Math. Floor (5/2)

Alternative approach

The stupidest way

function get()

{

    var s = 22.127456 + "";

    var str = s.substring(0,s.indexOf(".") + 3);

    alert(str);

}

 

2. Regular expressions work well

<script type="text/javascript">

onload = function(){

    var a = "23.456322";

    var aNew;

    var re = /([0-9]+.[0-9]{2})[0-9]*/;

    aNew = a.replace(re,"$1");

    alert(aNew);

}

</script>

He's smarter...

<script>

var num=22.127456;

alert( Math.round(num*100)/100);

</script>

5. Js keep 2 decimal places (mandatory)

For decimal places larger than 2, the above function is fine, but for decimal places smaller than 2, such as changeTwoDecimal(3.1), will return 3.1.

function changeTwoDecimal_f(x) {

    var f_x = parseFloat(x);

    if (isNaN(f_x)) {

        alert('function:changeTwoDecimal->parameter error');

        return false;

    }

    var f_x = Math.round(x * 100) / 100;

    var s_x = f_x.toString();

    var pos_decimal = s_x.indexOf('.');

    if (pos_decimal < 0) {

        pos_decimal = s_x.length;

        s_x += '.';

    }

    while (s_x.length <= pos_decimal + 2) {

        s_x += '0';

    }

    return s_x;

}

Function: round the floating point number to 2 places after the decimal point. If there are less than 2 places, fill 0.
This function returns the format usage of the string: changeTwoDecimal(3.1415926) returns 3.14 changeTwoDecimal(3.1) returns 3.10