eShop purchases made on the Nintendo Switch will be tied to your Nintendo Account, not the console you bought them on.
One of the most frustrating parts of Nintendo's digital storefront, the eShop, is that unlike competitors Sony and Microsoft, purchases made on a specific console are forever locked to that console. That means if your console dies, or you want to download a game on a friend's console, you're out of luck. Thankfully, it looks like Nintendo has finally reversed this policy with the Nintendo Switch, as the lucky fan who received his Switch two weeks early has revealed that eShop purchases on the Switch are tied to your Nintendo Account.
"Your Nintendo Account contains your Nintendo eShop purchase history and current balance. By re-linking your Nintendo Account after initializing the console, it will be possible to redownload any software or DLC purchased using that account. (Software that has been discontinued may not be available to redownload in some cases.)"
Welcome to 2005, Nintendo! Try not to innovate too much.