Joji questions

• TypeScript: is there a way to create a utility type to do minus calculation on numbers?
• confusions about how images are transferred via HTTP and handled in JavaScript
• React: why is the state returned from useState stays the same when the initializer function gets called on every re-render?
• Where in the ECMAScript specification can I find the reason about why {} !== {}?
• Why doesn't the default parameter being an empty array work with generic types?
• Jest: having trouble keeping a reference of a mock function with `jest.fn()`
• React: make a cycle-through component with both forward and backward directions using Generator
• JavaScript: weird bug when using Promises to load images in order
• Confusion about frame drops and requestAnimationFrame
• Confused about sending requests in HTTP1 and HTTP2

Joji answers