Flatten array to 1 line in JavaScript

Suppose, we have a nested array of numbers like this ?

const arr = [
   [ 0, 0, 0, -8.5, 28, 8.5 ],
   [ 1, 1, -3, 0, 3, 12 ],
   [ 2, 2, -0.5, 0, 0.5, 5.3 ]
];

We are required to write a JavaScript function that takes in one such nested array of numbers. The function should combine all the numbers in the nested array to form a single string.

In the resulting string, the adjacent numbers should be separated by whitespaces and elements of two adjacent arrays should be separated by a comma.

Using Traditional Loop Method

The code for this will be ?

const arr = [
   [ 0, 0, 0, -8.5, 28, 8.5 ],
   [ 1, 1, -3, 0, 3, 12 ],
   [ 2, 2, -0.5, 0, 0.5, 5.3 ]
];

const arrayToString = (arr = []) => {
   let res = '';
   for(let i = 0; i 

0 0 0 -8.5 28 8.5,1 1 -3 0 3 12,2 2 -0.5 0 0.5 5.3


Using map() and join() (One Line Solution)

Here's a more concise approach using array methods that can flatten the array to a string in just one line:

const arr = [
   [ 0, 0, 0, -8.5, 28, 8.5 ],
   [ 1, 1, -3, 0, 3, 12 ],
   [ 2, 2, -0.5, 0, 0.5, 5.3 ]
];

// One line solution
const result = arr.map(subArray => subArray.join(' ')).join(',');
console.log(result);


0 0 0 -8.5 28 8.5,1 1 -3 0 3 12,2 2 -0.5 0 0.5 5.3


How It Works

The one-line solution works by:

• Step 1: arr.map(subArray => subArray.join(' ')) - Convert each sub-array to a string with space-separated values
• Step 2: .join(',') - Join all the resulting strings with commas

Comparison

Conclusion

Both methods achieve the same result. The map().join() approach provides a cleaner, one-line solution that's more functional in style, while the traditional loop offers more explicit control over the process.