Solve - Object is possibly defined error in TypeScript

In this tutorial, we are going to learn about how to solve the Object is possibly defined error in TypeScript.

If we don’t provide any fallback value to the object property in TypeScript, it will show the following compile time error in the console.

Example:

const arr = [
  { a: 1, name: "Raju" },
  { b: 2, name: "John" },
];

const result = arr.find((el) => {
  return el.a === 1;
});

result.name.toLowerCase();

Output:

Object is possibly 'undefined'.

In the above code, we are accessing the result.name property which is not available untill it runs the arr.find() method, so by any chance if name property is not available in the object (eg: backend data is not available) we should provide some default value to handle it.

To solve the error, we can use the optional chaining (?) operator in TypeScript.

const arr = [
  { a: 1, name: "Raju" },
  { b: 2, name: "John" },
];

const result = arr.find((el) => {
  return el.a === 1;
});

result?.name.toLowerCase();

In the example above, we have used the optional chaining operator ?. So it checks implicitly if result is not null or undefined before it access to the result.name, if result is null or undefined, the expression short-circuts and returns undefined.

Alternatively, we can solve this error using if conditional check in TypeScript.

const arr = [
  { a: 1, name: "Raju" },
  { b: 2, name: "John" },
];

const result = arr.find((el) => {
  return el.a === 1;
});


if (result != undefined){
    console.log(result.name.toLowerCase()); // "raju"
}