Typescript custom type

custometype.tx

//JSON is way of communication between client and server

//custom type 
type Task={ 
	id: number;
	title: string;
	detail: string;
	createdAt: Date;
	updateAt: Date;
}

//declaration of array
var arr: Task[];

arr = [
	{
	id: 1234,
	title: "Mr D",
	detail: "Learning Array",
	createdAt: new Date(),
		updateAt: new Date()
	},
	{
	id: 1235,
	title: "Mr D",
	detail: "Learning Array",
	createdAt: new Date(),
		updateAt: new Date()
	},
	{
	id: 1236,
	title: "Mr D",
	detail: "Learning Array",
	createdAt: new Date(),
	updateAt: new Date()
	}

]

/**
 * array , id as an input
 * return the corresponding Task object
 */
function findTask(arr: Task[], id: number): Task| undefined { 
	//confusing
	//return tasks.find(task => task.id == id)
	for (var index = 0; index < arr.length; index++) { 
		if (arr[index].id == id)
			return arr[index];
	}
	return undefined;
}


console.log(findTask(arr,1236))