Strict mode is actually a combination of six other flags (as of TypeScript 3.8):

• noImplicitAny
• strictNullChecks (since 2.0)
• noImplicitThis (since 2.0)
• strictFunctionTypes (since 2.6)
• strictPropertyInitialization (since 2.7)
• strictBindCallApply (since 3.2)

Each option can be enabled or disabled separately. Some of them make TypeScript’s type checking better and some help make your code more readable and less error-prone.

You can enable strict mode in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
  }
}

You can disable any option that you don’t like from the strict family in the compileOptions as well (e.g. "noImplicitAny": false).

I think the most important flags are noImplicitAny and strictNullChecks. These two will really improve the type checking and readability of your code.

Let’s take a look at each flag.

#nodejs #javascript #typescript