用。（点）替换（逗号）和用（（逗号）替换。（点）

Question

I've a string as "1,23,45,448.00" and I want to replace all commas by decimal point and all decimal points by comma.

My required output is "1.23.45.448,00"

I've tried to replace , by . as follow:

var mystring = "1,23,45,448.00"
alert(mystring.replace(/,/g , "."));

But, after that, if I try to replace . by , it also replaces the first replaced . by , resulting in giving the output as "1,23,45,448,00"

Answer 1

Use replace with callback function which will replace , by . and . by , . The returned value from the function will be used to replace the matched value.

 var mystring = "1,23,45,448.00"; mystring = mystring.replace(/[,.]/g, function (m) { // m is the match found in the string // If `,` is matched return `.`, if `.` matched return `,` return m === ',' ? '.' : ','; }); //ES6 mystring = mystring.replace(/[,.]/g, m => (m === ',' ? '.' : ',')) console.log(mystring); document.write(mystring); 

Regex: The regex [,.] will match any one of the comma or decimal point.

String#replace() with the function callback will get the match as parameter( m ) which is either , or . and the value that is returned from the function is used to replace the match.

So, when first , from the string is matched

m = ',';

And in the function return m === ',' ? '.' : ','; return m === ',' ? '.' : ',';

is equivalent as

if (m === ',') {
    return '.';
} else {
    return ',';
}

So, basically this is replacing , by . and . by , in the string.

Answer 2

Nothing wrong with Tushar's approach, but here's another idea:

myString
  .replace(/,/g , "__COMMA__") // Replace `,` by some unique string
  .replace(/\./g, ',')         // Replace `.` by `,`
  .replace(/__COMMA__/g, '.'); // Replace the string by `.`