Is possible in js transform a String in this format

123456789

In something like this

*****6789

I want to use just one statment, something like this but keeping the last four characters.

var a = "12312312312123".replace(/[0-9]/g, "*")
console.log(a)

Is possible in js transform a String in this format

123456789

In something like this

*****6789

I want to use just one statment, something like this but keeping the last four characters.

var a = "12312312312123".replace(/[0-9]/g, "*")
console.log(a)

• javascript
• regex

5 Answers 5

you could make use of .(?=.{4}) with g flag:

var a = "12312312312123".replace(/.(?=.{4})/g, '*')
console.log(a)

Split the input into substrings, perform the replacement on the first part, and then append the second part.

var input = "123-456-7890";
var prefix = input.substr(0, input.length - 4);
var suffix = input.substr(-4);
var masked = prefix.replace(/\d/g, '*');
var a = masked + suffix;
console.log(a)

Use padStart

const str = '123456789';
console.log(str.slice(-4).padStart(str.length, '*'));

Or

const str = '123456789';
console.log(str.substr(-4).padStart(str.length, '*'));

A slightly different approach... by creating two capture groups and replacing the first with * repeated.

const a = '123456789'.replace(/(^\d+)(\d{4}$)/, (m,g1,g2) => '*'.repeat(g1.length) + g2);
console.log(a);

You can use either the function slice or function substr and the function padStart to fill * from left-to-right.

let str = "1234567893232323232";
console.log(str.slice(5, str.length).padStart(str.length, '*'));