Skip to main content

Type Assertion ↔ TS Syntax to override TSC's Type Inference for Static Type of specific Value

aka Assert

const inputEl = <HTMLInputElement\>document.getElementById("form-input")
const inputEl = document.getElementById("form-input") as HTMLInputElement
if (inputEl) {
  (inputEl as HTMLInputElement).value = "wasd"
}

Type Assertion removes Static Type safety, should avoid & use as last resort

Type Assertion ≠ Type Cast in other Programming Language

Type Cast​

aka type conversion of one type to another, in C/C++ - equiv to (implicit) type coersion or (explicit) reassignment in JS

Non-Null Assertion Operator​

postfix ! Type Assertion to Assert that Variable ≠ undefined || null

Source: Exclamation Mark In TypeScript | Become Front-End Expert

Type Assertion equivalent to Type Cast in other Programming Language, however, does not throw Exception or work at Runtime

as​

Type Assertion Type Operator to Assert Variable as Type

References​

  1. as ↔ Type Assertion Type Operator to Assert Variable as Type

  2. Non-Null Assertion Operator ↔ postfix ! Type Assertion to Assert that Variable ≠ undefined || null