Techniques for Modifying the Start and End of Strings in JavaScript

In JavaScript, there are several ways to modify the leading and trailing characters from strings. Let's explore some of the most commonly used methods.

1. String.padStart() method

String.padStart() method adds characters to the beginning of the string if its length is less than a certain length. It accepts two arguments: the length of the string should be and what string to add if it's not that long. The character to use is optional and defaults to a space.

let hour = "4";
let minute = "10";
let second = "8";

hour.padStart(2, "0"); //"04"
minute.padStart(2, "0"); //"10"
second.padStart(2, "0"); //"08"

2. String.padEnd() method

String.padEnd() method adds characters to the end of the string if smaller than a certain length. It accepts two arguments: the length of the string should be and what string to add if it's not that long. The character to use is optional and defaults to space.

let price1 = "20.50";
let price2 = "100.00";

price1.padEnd(6, "0"); //"20.500"
price2.padEnd(6, "0"); //"100.000"

3. String.trim() method

String.trim() method removes the leading and trailing white spaces from the string. This method is helpful when you need to get rid of unwanted spaces at the beginning or end of a string.

let str = "   I love JS.   ";
str.trim(); // Returns "I love JS."

4. String concatenation

You can add a string to the beginning or end of another string using the addition operator.

let sentence = "I love JavaScript";

sentence + ", and I love coding with it!";
// Output: "I love JavaScript, and I love coding with it!"