JavaScript: Convert a 2D array to a comma-separated values (CSV) string
JavaScript fundamental (ES6 Syntax): Exercise-257 with Solution
Write a JavaScript program to convert a 2D array to a comma-separated values (CSV) string.
- Use Array.prototype.map() and Array.prototype.join(delimiter) to combine individual 1D arrays (rows) into strings.
- Use Array.prototype.join('\n') to combine all rows into a CSV string, separating each row with a newline.
- Omit the second argument, delimiter, to use a default delimiter of ,.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const arrayToCSV = (arr, delimiter = ',') =>
arr.map(v => v.map(x => `"${x}"`).join(delimiter)).join('\n');
console.log(arrayToCSV([['a', 'b'], ['c', 'd']]));
console.log(arrayToCSV([['a', 'b'], ['c', 'd']], ';'));
Sample Output:
"a","b" "c","d" "a";"b" "c";"d"
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-257-1 by w3resource (@w3resource) on CodePen.
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JavaScript: Tips of the Day
Checking if a key exists in a JavaScript object?
Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined?
var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists!
You should instead use the in operator:
"key" in obj // true, regardless of the actual value
If you want to check if a key doesn't exist, remember to use parenthesis:
!("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj"
Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // true
Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj" Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty: obj.hasOwnProperty("key") // true For performance comparison between the methods that are in, hasOwnProperty and key is undefined.
Ref: https://bit.ly/2CFNp1X
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