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How to replace characters except last with the specified mask character in JavaScript ?

  • Last Updated : 17 Jun, 2021

In this article, we have given a number and the task is to replace the characters except for the last character with a specified mask character in JavaScript.

Example: Let’s take a number 12345678 and the masking character is * and the number of the last element that we have to skip is 2 In the below image shows that we skip the last two-element, and we mask another character with ‘*’

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Approach: We will make one function that can mask the character of the string except for the last element we will give our number as a string.

  • In this function we take three-argument, first one is a string which we want to mask, the second argument will specify mask character, and third is number of character that you want to skip
  • We use some inbuilt JavaScript function slice to slice our given string here we write slice(0,-n) where -n will skip the last n character of the string.
  • Then we use replace function to replace the character with a specified mask. Replace all characters we use regex /./g where ‘.’ will match any character and g is tens for globally.
  • Now we have to add the remaining character into the masking string, so we again use the slice function to get the remaining n character and add it into the masking string.




    // Function for masking the character 
    function MaskCharacter(str, mask, n = 1) {
        // Slice the string and replace with
        // mask then add remaining string
        return ('' + str).slice(0, -n)
            .replace(/./g, mask)
            + ('' + str).slice(-n);
    // Number that we want to mask 
    var num = 12345678;
    // Convert number into string
    var str = num.toString();
    // Call function without giving value of n
    console.log(MaskCharacter(str, '#'));
    // Call function with value of n
    console.log(MaskCharacter(str, '#', 2));


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