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980What Type Assertions Are
981The as Syntax
982Assertions Are Not Casts
983When DOM APIs Return Generic Types
984Asserting After Type Guards
985Non-Null Assertions with !
986Assertions for Third-Party Library Types
987Assertions with JSON.parse
988Const Assertions with as const
989When Assertions Are Legitimate
990The Readability Trade-off
991Prefer Type Guards Over Assertions
992Understanding Double Assertions
993When Single Assertions Fail
994The unknown Middle Step
995Overriding Incompatible Types
996Double Assertions as Red Flags
997Legitimate Use Cases
998Alternatives to Double Assertions
999Runtime Safety Considerations
1000DOM Element Access After getElementById

980What Type Assertions Are
981The as Syntax
982Assertions Are Not Casts
983When DOM APIs Return Generic Types
984Asserting After Type Guards
985Non-Null Assertions with !
986Assertions for Third-Party Library Types
987Assertions with JSON.parse
988Const Assertions with as const
989When Assertions Are Legitimate
990The Readability Trade-off
991Prefer Type Guards Over Assertions
992Understanding Double Assertions
993When Single Assertions Fail
994The unknown Middle Step
995Overriding Incompatible Types
996Double Assertions as Red Flags
997Legitimate Use Cases
998Alternatives to Double Assertions
999Runtime Safety Considerations
1000DOM Element Access After getElementById

Lesson 985 of 1,796·23. Type AssertionsPro lesson

Non-Null Assertions with !

The postfix `!` operator asserts a value is non-null/undefined, equivalent to `as NonNullable<typeof value>`.

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