Comprehensive Guide to Left-Pad Function Examples and Usage

The left-pad function is a useful utility in programming that allows you to pad a given string from the left side with a specific character. This functionality comes in handy in numerous scenarios, especially when dealing with fixed-width outputs. In this guide, we will explore several APIs of the left-pad library with code snippets, and also demonstrate an application example.

API Examples for Left-Pad

Basic Left Padding

This is the simplest form of left-padding a string:

 const leftPad = require('left-pad'); const result = leftPad('123', 5, '0'); console.log(result); // Outputs: 00123 

Left Padding with Different Characters

You can pad the string with different characters:

 const result = leftPad('123', 5, '*'); console.log(result); // Outputs: **123 

Left Padding with Spaces

Using spaces for padding:

 const result = leftPad('123', 5, ' '); console.log(result); // Outputs: "  123" 

Left Padding Non-String Values

Left-pad can be used with numbers as well, which are converted to strings:

 const result = leftPad(9, 3, '0'); console.log(result); // Outputs: 009 

Handling Edge Cases

Various edge cases such as input being already the desired length:

 const result = leftPad('12345', 5, '0'); console.log(result); // Outputs: 12345 (no padding needed) 

App Example Using Left-Pad

Let’s put it all together in a small application that formats account numbers:

 const leftPad = require('left-pad');
function formatAccountNumber(accountNumber) {
  return leftPad(accountNumber, 10, '0');
}
const accounts = [
  { name: 'Alice', number: 123 },
  { name: 'Bob', number: 4567 },
  { name: 'Charlie', number: 89 },
];
accounts.forEach(account => {
  console.log(`${account.name}: ${formatAccountNumber(account.number)}`);
}); // Outputs: // Alice: 0000000123 // Bob: 0000004567 // Charlie: 0000000089 

Through these examples, we have demonstrated how the left-pad function can be leveraged for a variety of padding tasks. This small utility is a powerful ally when consistent string formatting is required.

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