8ee50178f3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
27 lines
1.1 KiB
Markdown
27 lines
1.1 KiB
Markdown
### JSONtoCSV
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Converts an array of objects to a comma-separated values (CSV) string that contains only the `columns` specified.
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Use `Array.prototype.join(demiliter)` to combine all the names in `columns` to create the first row.
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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`.
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Use `Array.prototype.join('\n')` to combine all rows into a string.
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Omit the third argument, `delimiter`, to use a default delimiter of `,`.
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```js
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const JSONtoCSV = (arr, columns, delimiter = ',') =>
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[
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columns.join(delimiter),
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...arr.map(obj =>
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columns.reduce(
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(acc, key) => `${acc}${!acc.length ? '' : delimiter}"${!obj[key] ? '' : obj[key]}"`,
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''
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)
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)
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].join('\n');
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```
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```js
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JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b']); // 'a,b\n"1","2"\n"3","4"\n"6",""\n"","7"'
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JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b'], ';'); // 'a;b\n"1";"2"\n"3";"4"\n"6";""\n"";"7"'
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```
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