I have created an Angular pipe to suppress the sensitive information like credit cards, bank account, ABA numbers etc.

This is working fine but I would like to know if this is the best possible way to implement the logic.

Here is the Typescript code for pipe logic.

export class SuppressInfoPipe implements PipeTransform {

  transform(valueToSupress: string, unSuppressedCount?: number): string {

    let suppressedOutput = '';

    const valueToRemainUnsuppressed =
    valueToSupress.substring(valueToSupress.length - unSuppressedCount, valueToSupress.length);

    let astariskLength = valueToSupress.length - unSuppressedCount;

    for ( let i = 0; i < astariskLength; i++) {
     suppressedOutput = suppressedOutput.concat('*');
    suppressedOutput = suppressedOutput.concat(valueToRemainUnsuppressed);

    return suppressedOutput;


it takes the string input and the number of character they will no be hidden and then return the suppressed output.

Comments and suggestions are welcomed.


1 Answer 1


I would avoid the for loop to generate the "suppressed string".

My approach would be:

export class SuppressInfoPipe implements PipeTransform {

  transform(valueToSupress: string, unSuppressedCount = 0): string {
    const suppressedCount = valueToSupress.length - unSuppressedCount;
    const valueToRemainUnsuppressed =
    valueToSupress.substring(suppressedCount, valueToSupress.length);

    return Array(suppressedCount + 1).join('*') + valueToRemainUnsuppressed; // suppressedCount + 1: since join will a string of length "suppressedCount"

In this case:

Array(n) will return an array of length n.

enter image description here

.join("*") will join the list and return a string equivalent of length n-1.

  • \$\begingroup\$ That's much better. Only thing I want to confirm is this changing the type of Array object when returning just like JavaScript does to variables depending upon the data being assigned ? \$\endgroup\$ Mar 19, 2019 at 11:13
  • \$\begingroup\$ Updated my answer. \$\endgroup\$
    – Sree.Bh
    Mar 19, 2019 at 11:18
  • \$\begingroup\$ I got your point :) . Thanks for adding explanation to your answer. \$\endgroup\$ Mar 19, 2019 at 11:22

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