Breaking camelCase syntax in JavaScript

We need to write a JavaScript function that takes a camelCase string and converts it into a readable format by adding spaces before uppercase letters.

Our function should construct and return a new string that splits the input string using a space between words.

Problem Example

For example, if the input to the function is:

Input

const str = 'thisIsACamelCasedString';

Expected Output

'this Is A Camel Cased String'

Solution Using String Iteration

The approach iterates through each character and adds a space before uppercase letters (except the first character):

const str = 'thisIsACamelCasedString';

const breakCamelCase = (str = '') => {
    const isUpper = (char = '') => char.toLowerCase() !== char.toUpperCase() && char === char.toUpperCase();
    let res = '';
    const { length: len } = str;
    
    for(let i = 0; i 

this Is A Camel Cased String


Alternative Solution Using Regular Expression

A more concise approach using regex to match uppercase letters and replace them with a space plus the letter:

const str = 'thisIsACamelCasedString';

const breakCamelCaseRegex = (str = '') => {
    return str.replace(/([A-Z])/g, ' $1');
};

console.log(breakCamelCaseRegex(str));
console.log(breakCamelCaseRegex('javaScriptIsAwesome'));
console.log(breakCamelCaseRegex('HTMLParser'));


this Is A Camel Cased String
java Script Is Awesome
H T M L Parser


How It Works

The first solution uses a helper function isUpper() to check if a character is uppercase by comparing it with its lowercase and uppercase versions. It then iterates through the string and adds a space before each uppercase letter (except at the beginning).

The regex solution uses the pattern /([A-Z])/g to find all uppercase letters and replaces each with a space followed by the letter itself using ' $1'.

Comparison

Conclusion

Both methods effectively break camelCase strings into readable format. The regex approach is more concise and readable, while the iteration method offers better performance for large strings.