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30-seconds-of-code/snippets/join.md
30secondsofcode 709b3a31b7 Travis build: 2020
2018-05-02 17:21:29 +00:00

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### join
Joins all elements of an array into a string and returns this string. Uses a separator and an end separator.
Use `Array.reduce()` to combine elements into a string.
Omit the second argument, `separator`, to use a default separator of `','`.
Omit the third argument, `end`, to use the same value as `separator` by default.
```js
const join = (arr, separator = ',', end = separator) =>
arr.reduce(
(acc, val, i) =>
i === arr.length - 2
? acc + val + end
: i === arr.length - 1
? acc + val
: acc + val + separator,
''
);
```
```js
join(['pen', 'pineapple', 'apple', 'pen'], ',', '&'); // "pen,pineapple,apple&pen"
join(['pen', 'pineapple', 'apple', 'pen'], ','); // "pen,pineapple,apple,pen"
join(['pen', 'pineapple', 'apple', 'pen']); // "pen,pineapple,apple,pen"
```