by Pawan Kumar @jsartisan
In testing frameworks like Jest, a common feature is spyOn, which allows you to spy on methods of objects to see how they are called, and optionally replace them with a mock implementation.
Can you implement a simple version of spyOn that allows you to track calls to a method on an object?
Your spyOn function should:
- Take an object and the name of the method to spy on.
- Replace the original method with a spy function that records each call.
- Provide a way to restore the original method.
const obj = {
greet(name) {
return `Hello, ${name}!`;
}
};
const spy = spyOn(obj, 'greet');
obj.greet('Alice'); // Call the method
console.log(spy.calls); // Should output: [['Alice']]
console.log(spy.results); // Should output: ['Hello, Alice!']
spy.restore(); // Restore the original method
console.log(obj.greet('Bob')); // Should output: 'Hello, Bob!'Implement the spyOn function and ensure it behaves as described.
