JavaScript Program to Remove Whitespace from String

You can remove all whitespace from a string in JavaScript using str.replace(/\s+/g, ''), which replaces all spaces, tabs, and newlines with nothing.

Examples

Inputhello world

Outputhelloworld

Input JavaScript is fun

OutputJavaScriptisfun

Input spaced text

Outputspacedtext

How to Think About It

To remove whitespace from a string, think about finding all spaces, tabs, and newlines and then deleting them. We can do this by searching for any whitespace character and replacing it with nothing, effectively removing it.

Algorithm

1

Get the input string.

2

Find all whitespace characters in the string.

3

Replace each whitespace character with an empty string.

4

Return the cleaned string without any whitespace.

Code

javascript

function removeWhitespace(str) {
  return str.replace(/\s+/g, '');
}

const input = "  Hello  World \t";
const output = removeWhitespace(input);
console.log(output);

Output

HelloWorld

Dry Run

Let's trace the input string " Hello World \t" through the code.

1

Input string

" Hello World \t"

2

Apply replace with regex /\s+/g

All spaces and tab characters matched: " ", " ", " \t"

3

Replace all matched whitespace with ''

Resulting string: "HelloWorld"

Original String	Whitespace Found	Result After Replacement
Hello World	spaces and tab	HelloWorld

Why This Works

Step 1: Use of regex \s

The \s pattern matches any whitespace character like spaces, tabs, and newlines.

Step 2: Global flag g

The g flag makes sure all whitespace occurrences in the string are replaced, not just the first one.

Step 3: Replacing with empty string

Replacing matched whitespace with '' removes them completely from the string.

Alternative Approaches

Using split and join

javascript

function removeWhitespace(str) {
  return str.split(/\s+/).join('');
}

console.log(removeWhitespace(' a b c '));

This splits the string by whitespace and joins parts without spaces; slightly less direct but easy to understand.

Using loop and manual check

javascript

function removeWhitespace(str) {
  let result = '';
  for (const char of str) {
    if (char !== ' ' && char !== '\t' && char !== '\n') {
      result += char;
    }
  }
  return result;
}

console.log(removeWhitespace(' a b c '));

Manually checks each character; more code but good for learning how to filter characters.

Complexity: O(n) time, O(n) space

Time Complexity

The program scans each character once to find whitespace, so it runs in linear time relative to string length.

Space Complexity

A new string is created without whitespace, so space used is proportional to the input size.

Which Approach is Fastest?

Using replace with regex is usually fastest and most concise compared to splitting or manual loops.

Approach	Time	Space	Best For
Regex replace	O(n)	O(n)	Quick and concise removal of all whitespace
Split and join	O(n)	O(n)	Readable alternative, good for beginners
Manual loop	O(n)	O(n)	Learning character filtering, less concise