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Disallow non-null assertions using the ! postfix operator.


Some problems reported by this rule are manually fixable by editor suggestions.

TypeScript's ! non-null assertion operator asserts to the type system that an expression is non-nullable, as in not null or undefined. Using assertions to tell the type system new information is often a sign that code is not fully type-safe. It's generally better to structure program logic so that TypeScript understands when values may be nullable.

module.exports = {
"rules": {
"@typescript-eslint/no-non-null-assertion": "warn"


interface Example {
property?: string;

declare const example: Example;
const includesBaz =!.includes('baz');


This rule is not configurable.

When Not To Use It

If your project does not use the strictNullChecks compiler option, this rule is likely useless to you. If your code is often wildly incorrect with respect to strict null-checking, your code may not yet be ready for this rule.