Splitting string into groups – JavaScript

Given a string S, consisting of alphabets, numbers and special characters. We need to write a program to split the strings in three different strings S1, S2 and S3, such that −

• The string S1 will contain all the alphabets present in S,
• The string S2 will contain all the numbers present in S, and
• S3 will contain all special characters present in S.

The strings S1, S2 and S3 should have characters in the same order as they appear in input.

Syntax

const separateCharacters = str => {
    return str.split("").reduce((acc, val) => {
        // Logic to categorize each character
        return acc;
    }, { numbers: '', alpha: '', special: '' });
};

Example

The following example demonstrates how to separate a string into alphabets, numbers, and special characters:

const str = "Th!s String C0nt@1ns d1fferent ch@ract5rs";
const separateCharacters = str => {
    const strArr = str.split("");
    return strArr.reduce((acc, val) => {
        let { numbers, alpha, special } = acc;
        if (+val) {
            numbers += val;
        } else if (val.toUpperCase() !== val.toLowerCase()) {
            alpha += val;
        } else {
            special += val;
        }
        return { numbers, alpha, special };
    }, {
        numbers: '',
        alpha: '',
        special: ''
    });
};
console.log(separateCharacters(str));

{
    numbers: '0115',
    alpha: 'ThsStringCntnsdfferentchractrs',
    special: '! @  @'
}

How It Works

The algorithm uses three key techniques to categorize characters:

• Number Detection: Uses +val to check if a character converts to a truthy number
• Alphabet Detection: Compares val.toUpperCase() !== val.toLowerCase() to identify letters
• Special Characters: Everything else falls into this category (spaces, symbols, punctuation)

Alternative Approach Using Regular Expressions

const str = "Hello123!@# World456$%^";
const separateWithRegex = str => {
    return {
        alpha: str.replace(/[^a-zA-Z]/g, ''),
        numbers: str.replace(/[^0-9]/g, ''),
        special: str.replace(/[a-zA-Z0-9]/g, '')
    };
};
console.log(separateWithRegex(str));

{
    alpha: 'HelloWorld',
    numbers: '123456',
    special: '!@# $%^'
}

Comparison

Conclusion

Both approaches effectively separate strings into alphabets, numbers, and special characters while maintaining order. The reduce method offers more control, while regex provides cleaner, more concise code for simple categorization tasks.