How to convert a 2D array to a comma-separated values (CSV) string in JavaScript ?
Last Updated : 28 May, 2024
Given a 2D array, we have to convert it to a comma-separated values (CSV) string using JS.
Input:
[ [ "a" , "b"] , [ "c" ,"d" ] ]
Output:
"a,b
c,d"
Input:
[ [ "1", "2"]
["3", "4"]
["5", "6"] ]
Output:
"1,2
3,4
5,6"
To achieve this, we must know some array prototype functions which will be helpful in this regard:
Join function: The Array.prototype.join( ) function is used to join all the strings in an array with a character/string.
Example:
[ "a","b"].join( ",") will result in : "a,b"
Map function: The Array.prototype.map() returns a new array with the results of calling a function that we provide, on each element.
Example:
arr= ["a","b"]
// Adding "c" to each element
newArray = arr.map( item => item + "c")
value of newArray = ["ac", "bc"]
Approach: We will use the map function and join function to combine each 1D row into a string with the separation of a comma. and then join all the individual strings with "\n", using the join function.
Example: In this example, we will be using the map() and join() functions to convert the CSV values to strings.
JavaScript <script> // Create CSV file data in an array var array2D = [ [ "a" , "2"] , [ "c" ,"d" ] ]; // Use map function to traverse on each row var csv = array2D .map((item) => { // Here item refers to a row in that 2D array var row = item; // Now join the elements of row with "," using join function return row.join(","); }) // At this point we have an array of strings .join("\n"); // Join the array of strings with "\n" console.log(csv); </script> Output:
a,2
c,d
Explanation: We first used the map function on the 2D array to traverse each row, then we used the join function to join the array of elements in that row using a comma. Next, that map function returns an array of strings, which we join by using "\n". Thus resulting in a CSV string.
Alternative Approach: We can even use for loops to traverse in the array, instead of a map.
Example: In this example, we will be using the javascript loops to convert the CSV to strings.
JavaScript <script> var csv=""; //create CSV file data in an array var array2D = [ [ "a" , "2"] , [ "c" ,"d" ] ]; for (var index1 in array2D) { var row = array2D[index1]; // Row is the row of array at index "index1" var string = ""; // Empty string which will be added later for (var index in row) { // Traversing each element in the row var w = row[index]; // Adding the element at index "index" to the string string += w; if (index != row.length - 1) { string += ","; // If the element is not the last element , then add a comma } } string += "\n"; // Adding next line at the end csv += string; // adding the string to the final string "csv" } console.log(csv); </script> Output:
a,2
c,d
Alternative Approach: Another approach to convert a 2D array to a CSV string is to use the Array.prototype.reduce() method.
- Use the reduce() method to iterate over each row of the 2D array.
- Inside the reduce() callback function, use the join() method to concatenate the elements of each row with a comma.
- Append a newline character \n after each row.
- Concatenate the result strings of each row iteration
Example:
JavaScript // Create CSV file data in an array var array2D = [ [ "a" , "2"] , [ "c" ,"d" ] ]; // Use reduce function to traverse each row and convert to CSV format var csv = array2D.reduce((acc, row) => { // Join elements of the row with comma separator let rowString = row.join(","); // Add a newline character after each row rowString += "\n"; // Concatenate the result strings of each row iteration return acc + rowString; }, ""); console.log(csv); This approach simplifies the code by combining the iteration and string concatenation logic within the reduce() method, resulting in concise and readable code.