Assertion Functions की जानकारी

function assert(condition: boolean, msg: string): asserts condition {
  if (!condition) throw new Error(msg);
}
const x: number | undefined = 5;
assert(x !== undefined, "x must be defined");
console.log(x + 1);

interface User {
  name: string;
}
function assertIsUser(value: any): asserts value is User {
  if (typeof value?.name !== "string") throw new Error("Not a user");
}
const data: any = { name: "Ravi" };
assertIsUser(data);
console.log(data.name);

function assertExists<T>(value: T | null, msg: string): asserts value is T {
  if (value === null) throw new Error(msg);
}
const config: { key: string } | null = { key: "value" };
assertExists(config, "config must be loaded");
console.log(config.key);

function assertPositive(n: number): asserts n is number {
  if (n <= 0) throw new Error("value must be positive, got " + n);
}
const balance = 10;
assertPositive(balance);
console.log("Balance ok:", balance);

function isPositive(n: number): boolean {
  return n > 0;
}
function assertPositive(n: number): asserts n is number {
  if (n <= 0) throw new Error("must be positive");
}
console.log(isPositive(-1));
assertPositive(5);
console.log("passed assertion");