How do you create a constructor function?

To create a constructor function in JavaScript, define a regular function with a capitalized name to indicate it's a constructor. Use the this keyword to set properties and methods. When creating an instance, use the new keyword.

function Person(name, age) {
  this.name = name;
  this.age = age;
}

const john = new Person("John", 30);
console.log(john.age); // 30