Avoid negating the left operand of relational operators

Metadata

ID: javascript-best-practices/no-unsafe-negation

Language: JavaScript

Severity: Warning

Category: Best Practices

Negation of the left-hand side of an expression is often unintended.

!a in b
(!a in b)
!(a) in b
!a instanceof b
(!a instanceof b)
!(a) instanceof b

a in b
a in b === false
!(a in b);
(!a) in b
a instanceof b
a instanceof b === false;
!(a instanceof b);
(!a) instanceof b;

1
2
rulesets:
  - javascript-best-practices     # Rules to enforce JavaScript best practices.

Create a static-analysis.datadog.yml with the content above at the root of your repository
Use our free IDE Plugins or add Code Analysis scans to your CI pipelines
Get feedback on your code

For more information, please read the Code Analysis documentation

Identify code vulnerabilities directly in your
VS Code editor

Identify code vulnerabilities directly in
JetBrains products