base questions

`String.prototype.split` splits a string into an array of substrings based on a specified separator. The separator can be a string or regular expression. 

const str = 'a,b,c';
const arr = str.split(',');
console.log(arr); // ['a', 'b', 'c']

`String.prototype.substr` extracts a substring from a string based on a starting index and length. It returns the extracted substring. 

const str = 'hello world';
const substr = str.substr(6, 5);
console.log(substr); // 'world'

Routing in Angular is implemented using the Router module, which provides a way to navigate between different components based on URL paths. To set up routing, you first import `RouterModule` and `Routes` from `@angular/router` in your Angular module. You then define an array of routes that map URL paths to components. This configuration is passed to the `RouterModule.forRoot()` method in the module's imports array. The `<router-outlet>` directive is used in the template to specify where the routed components should be displayed. This setup allows for seamless navigation and dynamic content rendering within the application.

Django includes a testing framework based on Python's `unittest` module. You write test cases by creating classes that inherit from `django.test.TestCase`. These tests can simulate requests, check responses, and verify the behavior of your application’s components. Run tests using `python manage.py test` to ensure your application works as expected.

The DATEDIF function calculates the difference between two dates based on a specified unit. For example, =DATEDIF(A1, B1, 'D') returns the number of days between the dates in A1 and B1. You can also use 'M' for months or 'Y' for years. This function is useful for calculating age, tenure, or duration.

The OFFSET function can be used to create dynamic ranges by adjusting its reference based on specified rows and columns. For example, =OFFSET(A1, 2, 3, 5, 5) creates a range starting 2 rows down and 3 columns over from A1, with a height of 5 rows and a width of 5 columns. This is useful for creating dynamic named ranges or adaptable formulas.

The PMT function calculates the payment for a loan based on constant payments and a constant interest rate. For example, =PMT(0.05/12, 360, 200000) calculates the monthly payment for a $200,000 loan at a 5% annual interest rate over 30 years. This function is useful for financial planning and loan calculations.

`useReducer` is a hook used in React Native to manage complex state logic in functional components. It works similarly to Redux's reducer, allowing you to manage state transitions through actions. It is useful for managing state that involves multiple sub-values or when the next state depends on the previous one. It provides better performance and clarity for complex state interactions.

In Vue.js, a computed property is a property that is automatically recalculated based on reactive data dependencies. Computed properties are defined in the `computed` option of a Vue component and are used for performing calculations or transformations of data. Unlike methods, computed properties are cached based on their dependencies, meaning they are only recalculated when the dependent data changes. This makes computed properties efficient for scenarios where derived data needs to be computed from existing state.

Vue.js dynamic components allow you to switch between different components dynamically based on conditions. This is achieved using the `component` element along with the `:is` attribute, which can take a component name or component definition. For example, `<component :is='currentComponent'></component>` will render the component specified by `currentComponent`. Dynamic components are useful for scenarios where you need to render different components based on user interactions or application state without having to manage multiple static components.