Reversing the order of words of a string in JavaScript

We are required to write a JavaScript function that takes in a string as the only argument.

The function should reverse the order of the words in the string and return the new string.

The only condition is that we cannot use the inbuilt array method reverse().

For example −

If the input string is −

const str = 'this is a string';

Then the output string should be −

string a is this

Using Manual Array Reversal

We can split the string into words, manually reverse the array without using the built-in reverse() method, and join back:

const str = 'this is a string';

const reverseWordOrder = (str = '') => {
    const strArr = str.split(' ');
    let temp = '';
    const { length } = strArr;
    
    // Manually reverse array by swapping elements
    for(let i = 0; i < length / 2; i++){
        temp = strArr[i];
        strArr[i] = strArr[length - 1 - i];
        strArr[length - 1 - i] = temp;
    }
    
    return strArr.join(' ');
};

console.log(reverseWordOrder(str));

string a is this

Using Loop to Build Reversed String

Another approach is to iterate through the words array from the end to the beginning:

const str = 'hello world javascript programming';

const reverseWordOrderLoop = (str = '') => {
    const words = str.split(' ');
    let reversed = '';
    
    // Build string from last word to first
    for(let i = words.length - 1; i >= 0; i--){
        reversed += words[i];
        if(i > 0) reversed += ' '; // Add space except for last word
    }
    
    return reversed;
};

console.log(reverseWordOrderLoop(str));

programming javascript world hello

Comparison

Conclusion

Both methods effectively reverse word order without using the built-in reverse() method. The loop approach is more readable, while manual reversal demonstrates array manipulation techniques.