How to map through an array in React without ids?

Question

I have a fairly standard array:

["value","value","value"]

If I want to iterate through it, each list item needs a unique key. But how would I do this in this case?

JSONs often come with an id -but in this case I don't have any id's, and the values also aren't unique, so I cannot just use them as the key.

{someArray.map(object => {
                return (<span key=???> {object} </span>); })}

Answer 1

You can use the second argument of map, the index:

{someArray.map((object, i) => {
                return (<span key={i}> {object} </span>); })}

As long as someArray remains the same during the lifetime of the component, this is fine; if not, it will cause more re-rendering than necessary when you move, insert or remove items, because all the props of the child change (but in this case you will not notice it at all).