JavaScript: Convert an array of objects to a comma-separated values string that contains only the columns specified
JavaScript fundamental (ES6 Syntax): Exercise-5 with Solution
Write a JavaScript program to convert an array of objects to a comma-separated values (CSV) string that contains only the columns specified.
- Use Array.prototype.join(delimiter) to combine all the names in columns to create the first row.
- Use Array.prototype.map() and Array.prototype.reduce() to create a row for each object, substituting non-existent values with empty strings and only mapping values in columns.
- Use Array.prototype.join('\n') to combine all rows into a string.
- Omit the third argument, delimiter, to use a default delimiter of,.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const JSON_to_CSV = (arr, columns, delimiter = ',') =>
[
columns.join(delimiter),
...arr.map(obj =>
columns.reduce(
(acc, key) => `${acc}${!acc.length ? '' : delimiter}"${!obj[key] ? '' : obj[key]}"`,
''
)
)
].join('\n');
console.log(JSON_to_CSV([{ x: 100, y: 200 }, { x: 300, y: 400, z: 500 }, { x: 6 }, { y: 7 }], ['x', 'y']));
console.log(JSON_to_CSV([{ x: 100, y: 200 }, { x: 300, y: 400, z: 500 }, { x: 6 }, { y: 7 }], ['x', 'y'], ';'));
Sample Output:
x,y "100","200" "300","400" "6","" "","7" x;y "100";"200" "300";"400" "6";"" "";"7"
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-1-5 by w3resource (@w3resource) on CodePen.
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Previous: Write a JavaScript program to convert a comma-separated values (CSV) string to a 2D array of objects. The first row of the string is used as the title row.
Next: Write a JavaScript program to target a given value in a nested JSON object, based on the given key.
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JavaScript: Tips of the Day
Chunks an array into n smaller arrays
Example:
const tips_chunkIntoN = (arr, n) => { const size = Math.ceil(arr.length / n); return Array.from({ length: n }, (v, i) => arr.slice(i * size, i * size + size) ); } console.log(tips_chunkIntoN([1, 2, 3, 4, 5, 6, 7,8], 4));
Output:
[[1,2],[3,4],[5,6],[7,8]]
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