In TypeScript, you can get the index of an element in an array using the indexOf() method. Here is an example:
const myArray: string[] = ["apple", "banana", "orange"];
const index = myArray.indexOf("banana");
console.log(index); // Output: 1
In this example, we declare an array called myArray and assign it three string values. We then use the indexOf() method to find the index of the string "banana" in the array. The indexOf() method returns the index of the element if it exists in the array, or -1 if it doesn't.
You can also use the findIndex() method to find the index of an element that matches a condition. Here is an example:
interface Person {
name: string;
age: number;
}
const people: Person[] = [
{ name: "Alice", age: 25 },
{ name: "Bob", age: 30 },
{ name: "Charlie", age: 35 },
];
const index = people.findIndex(person => person.name === "Bob");
console.log(index); // Output: 1
In this example, we declare an array of objects representing people. We then use the findIndex() method to find the index of a person object that has a name property equal to "Bob". The findIndex() method takes a callback function that returns true if the condition is met, and returns the index of the first element that meets the condition. If no elements meet the condition, it returns -1.