different-variables-types

In JavaScript, you can assign any value to any variable. But in TypeScript, a variable's type is generally fixed. Using different variables for different concepts improves type safety and code clarity.

Union types are harder to work with and obscure the code's intent.

const makes code easier for both humans and TypeScript to understand.

当想要重用变量时使用。当变量改变类型时使用。将联合类型用于多种目的时使用。 来源：marius-townhouse/effective-typescript-skills。