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Function: assertCondition

core.assertCondition

assertCondition(condition, message?): asserts condition

Helper to apply a TypeScript assertion to subsequent code. TypeScript can infer type information from many expressions, and this helper applies those inferences to all code that follows call to this function.

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions

Example

function foo(value: string | number) {
  assertCondtion(typeof value === 'string');
  // TypeScript would otherwise compalin, because `value` could have been number,
  // but the above assertion refines the type based on the `typeof` expression.
  return value.toUpperCase();
}

Parameters

Name Type
condition any
message? string

Returns

asserts condition

Defined in

helpers/ensure.ts:79