noImplicitAny

noImplicitAny reports locations where the compiler would otherwise infer the unsafe any type without an explicit annotation. Function parameters, callbacks without contextual types, and loosely declared variables are common examples. Prefer specific types or unknown at an external-data boundary.

Both parameters have explicit numeric types; the return type remains numeric. Removing the annotation from percent produces an implicit-any diagnostic with noImplicitAny.

Annotating everything as any makes the errors disappear but forfeits the guarantees that motivated the option.

Save as noimplicitany.ts. The following program passed strict TypeScript compilation, and the displayed output was captured by executing its emitted JavaScript with Node.js 22.16.0.

TypeScript source

function discount(price: number, percent: number): number {
  return price * (1 - percent / 100);
}
console.log(discount(100, 15).toFixed(2));

Verified output

85.00

Compile: npx tsc --strict --target es2022 --module commonjs noimplicitany.ts; run: node noimplicitany.js. For Node.js API examples, install @types/node first. For browser projects, use the browser-specific instructions below.

The example demonstrates the code-level behavior; the related configuration or test commands are shown separately when needed.

Both parameters have explicit numeric types; the return type remains numeric. Removing the annotation from percent produces an implicit-any diagnostic with noImplicitAny.

Predict what changes if you alter one input. Then run the code to compare your reasoning with the real output.

Annotating everything as any makes the errors disappear but forfeits the guarantees that motivated the option.

Identify whether the failure is a type-checking issue, a configuration issue, or a runtime behavior issue before choosing a fix.

Delete one parameter annotation and use tsc --noImplicitAny --noEmit to inspect the diagnostic.

Write down your expected result first. For configuration examples, compare compiler output and diagnostics; for test examples, make the assertion fail deliberately to verify that the tool reports it.

For the exact current options and platform behavior, consult the official documentation. These examples were verified using the tool versions described above.

noImplicitAny reports locations where the compiler would otherwise infer the unsafe any type without an explicit annotation.

Run the primary example, then complete the practice task or environment-specific lab.