How to change the value of an item in localstorage using Javascript [duplicate]

Answer 1

You retrieve the JSON, parse it, update the object you get from parsing it, stringify the result, and store that result:

const ship = JSON.parse(localStorage.getItem("ship"));
ship.name = "newName";
localStorage.setItem("ship", JSON.stringify(ship));

If you want to do it all in one line (although I don't recommend it, it's harder to read, maintain, and debug that way; leave minification to minifiers):

localStorage.setItem("ship", JSON.stringify(Object.assign(JSON.parse(localStorage.getItem("ship")), {name: "newName"})));