# JavaScript (ES6), 14 bytes

Takes input as an array of 2 strings. Inspired by [Luis' answer][1].

<!-- language-all: lang-javascript -->

 JSON.stringify

[Try it online!][TIO-k12e1pq4]

[JavaScript (Node.js)]: https://nodejs.org
[TIO-k12e1pq4]: https://tio.run/##y0osSyxOLsosKNHNy09J/Z9m@98r2N9Pr7ikKDMvPTOt8n9yfl5xfk6qXk5@ukaaRrRSRmpOTr6SjoJSeX5RTopSrKYmF7qSRJB0UjIOyaRkkDRY8j8A "JavaScript (Node.js) – Try It Online"


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# JavaScript (ES6), <s>&nbsp;21&nbsp;</s> 20 bytes

Takes input as `(a)(b)`.

<!-- language-all: lang-javascript -->

 a=>b=>[a.length,a]+b

[Try it online!](https://tio.run/##bcq7DYAgEADQ3jGoICobwCLG4vhrLpwBouNjaI31eyfcUG05rrZmcr4H1UFpo/QGEn2OLS2wz6ZbypXQS6TIA2fJIxITnD1U0DEhpk@Agcb@krEDB/UX "JavaScript (Node.js) – Try It Online")

Returns the length of \$a\$, followed by a comma, followed by the concatenation of \$a\$ and \$b\$.


 [1]: https://codegolf.stackexchange.com/a/193645/58563