JS Format string

In Delphi with object pascal, or in Visual Studio with C#, methods exist to concatenate different data types into a string. Wouldn’t it be nice to have a similar method in JavaScript? And what would the advantage be of such a method?


  • Use the same variable multiple times
  • Gets the string value of any data type
  • Apply special formatting (date/time/currency)
  • Apply padding (left, right, special fill character)

JS Format string method

function FormatString(str, ...val) { 
    for (let index = 0; index < val.length; index++) {
        str = str.replace("{"+ index + "}", val[index]);
    return str;

Example to use the format string method

console.log(FormatString("/search?country={0}&province={1}&city={2}","nl_NL", "Overijssel", "Zwolle"));

The result looks like:


You can use an online playground to test the code above.