How do I FirstOrDefault in Javascript?

The javascript find function returns either The first item that satisfies the condition or undefined. This means that it behaves like a FirstOrUndefined function.

Consider this list with names:

let names = ["vera", "chuck", "dave"];

Here’s the code where two items match the condition. The first one will be returned:

console.log(names.find(x => x.length === 4));

result:

vera

Here’s the code where none of the items match the condition. undefined will be returned:

console.log(names.find(x => x === "ringo"));

result:

undefined

This might be interesting to you, especially if you are used to typing C# code, where the result for nothing-found is null. Checking for null does not work when checking the result for find in Javascript.

Check the result

Here’s the same list and a new variable vera that points to one of the items:

let names = ["vera", "chuck", "dave"];
let vera = names.find(x => x === "vera");

You can check for vera !== undefined like this:

if (vera !== undefined) {
console.log('found vera');
}

or since undefined is a falsy value, you can omit the !== undefined part

if (vera) {
console.log('found vera');
}

Conclusion

The javascript find function is incredibly powerful and saves you the trouble of looping though items to find an object manually.

I’ve also written about FirstOrDefault in Python and I recommend checking out how it works in that language.