Black Knight Interview Question

JavaScript - 1.What is undefined and null ? 2.What is callback function ? 3.Write a piece of code for the list of object showing the employees less than 20,000? 4.Write the piece of code showing the iteration of array element in console? Angular 1. What is Databinding 2. What is Lazy Loading 3. Write the piece of code for Api Integration using services ? 4. What is Lifecycle Hooks ? 5. How to share or transfer data between Components ?Explain it briefly