Static Analysis and Linting

Static analysis reviews code without executing every path. TypeScript type checking and lint rules detect different classes of defects, such as incompatible types versus suspicious patterns. Configure relevant rules for the project and handle noise deliberately, rather than disabling every difficult diagnostic.

readonly communicates that total should not mutate its input. TypeScript checks those operations. A linter can additionally enforce conventions and flag suspicious unused variables.

A lint warning is not necessarily a runtime failure; neither linting nor type checking replaces tests of actual behavior.

Save as static-analysis-linting.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 total(scores: readonly number[]): number {
  return scores.reduce((sum, value) => sum + value, 0);
}
console.log(total([4, 5, 6]));

Verified output

15

Compile: npx tsc --strict --target es2022 --module commonjs static-analysis-linting.ts; run: node static-analysis-linting.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.

readonly communicates that total should not mutate its input. TypeScript checks those operations. A linter can additionally enforce conventions and flag suspicious unused variables.

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

A lint warning is not necessarily a runtime failure; neither linting nor type checking replaces tests of actual behavior.

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

Configure noUnusedLocals and a linter rule for unused variables, then compare the messages from both tools.

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.

Static analysis reviews code without executing every path.

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