Allocation Result Ignored

ID

javascript.allocation_result_ignored

Severity

low

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

JavaScript

Tags

code-smell, dead-code

Description

Reports new expressions used as a free-standing statement, where the constructed object is neither assigned, returned, nor passed anywhere.

// Bad
new EventListener(target, fn);
new Logger();

Rationale

If the result of new is discarded, the program is using the constructor purely for its side effects — registering a listener, mutating shared state, opening a connection. That pattern is hard to read (the side effect is hidden behind an allocation that looks like it should produce a value) and easy to break later when someone "cleans up" the unused object.

It is also a common pattern of dead code: a refactor extracted the work into a function but left the original new behind.

Remediation

If the constructor is doing real work, replace the allocation with an explicit factory call or a top-level function:

// Good — name the action being performed.
EventListener.attach(target, fn);
configureLogger();

If the result is genuinely needed (e.g. to be released later), capture it in a variable:

// Good
const listener = new EventListener(target, fn);
// ... later
listener.detach();

If the line is dead code, delete it.

References