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30-seconds-of-code/snippets/mask.md
Angelos Chalaris 931e9c689f Archive, multitagging, cleanup
Cleaned up the current snippets for consistency and minor problems, added multiple tags to most of them, archived a few.
2018-01-05 16:33:54 +02:00

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### mask
Replaces all but the last `num` of characters with the specified mask character.
Use `String.slice()` to grab the portion of the characters that need to be masked and use `String.replace()` with a regexp to replace every character with the mask character.
Concatenate the masked characters with the remaining unmasked portion of the string.
Omit the second argument, `num`, to keep a default of `4` characters unmasked. If `num` is negative, the unmasked characters will be at the start of the string.
Omit the third argument, `mask`, to use a default character of `'*'` for the mask.
```js
const mask = (cc, num = 4, mask = '*') =>
('' + cc).slice(0, -num).replace(/./g, mask) + ('' + cc).slice(-num);
```
```js
mask(1234567890); // '******7890'
mask(1234567890, 3); // '*******890'
mask(1234567890, -4, '$'); // '1234$$$$$$'
```