Avoid extra non-null assertions
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ID: typescript-best-practices/no-extra-non-null-assertion
Language: TypeScript
Severity: Error
Category: Error Prone
Description
The non null
or undefined
assertion operation should not be used twice in a single expression.
Non-Compliant Code Examples
const bar = foo!!.bar;
function foo(bar: number | undefined) { const bar: number = bar!!; }
function foo(bar?: { n: number }) { return bar!?.n; }
function foo(bar?: { n: number }) { return bar!?.(); }
// parentheses
const foo: { bar: number } | null = null; const bar = (foo!)!.bar;
function foo(bar?: { n: number }) { return (bar!)?.n; }
function foo(bar?: { n: number }) { return (bar)!?.n; }
function foo(bar?: { n: number }) { return (bar!)?.(); }
Compliant Code Examples
const bar = foo!.bar;
function foo(bar: number | undefined) {
const bar: number = bar!;
}
function foo(bar?: { n: number }) {
return bar?.n;
}
// https://github.com/typescript-eslint/typescript-eslint/issues/2166
checksCounter?.textContent!.trim();
// https://github.com/typescript-eslint/typescript-eslint/issues/2732
function foo(key: string | null) {
const obj = {};
return obj?.[key!];
}
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