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String Pad in JavaScript

Samantha Ming on August 12, 2020

It's super easy to pad a string! Just pass in your desired string and length. The string will be padded until the length has been met. Use padSta...

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Functional Javascript • Aug 12 '20 • Edited

Excellent work Samantha.

A couple of these might come in handy so I utility-ized them...

Utility 1

/**
@func
pretty format two columns as a text-based table

@param {string[][]} a
@return {string} multiline formatted str
*/
const formatTwoCol = a => a.map(([col1, col2]) => col1 + col2.padStart(20 - col1.length)).join("\n");

//@tests
const purchaseItems = [
  ["Masks", "9.99"],
  ["Shirt", "20.00"],
  ["Jacket", "200.00"],
  ["Gloves", "10.00"],
];

console.log(formatTwoCol(purchaseItems));
/*
output:
Masks           9.99
Shirt          20.00
Jacket        200.00
Gloves         10.00

*/

Utility 2

/**
@func
mask a credit card number with asterisks

@tags
security

@algor
get last 4 numbers
- then left-pad these 4 numbers with asterisks
- by the count of the remaining numbers

@param {string} cc - Credit Card number as a string, space separated per 4 digits
@return {string} - masked str
*/
const maskCreditCardNumber = cc => cc.slice(-4).padStart(cc.length, "*");

//@tests
console.log(maskCreditCardNumber("2222 2222 2222 2222"));
/*
output:
***************2222

*/

Samantha Ming • Aug 13 '20

WHoa! these are fantastic 👏 Thanks for sharing 🙌

scroung720 • Aug 13 '20

This is an amazing article. Great writing. Keep it up!

Samantha Ming • Aug 17 '20

You bet!! thanks for the encouraging words 💪