Function assertDefinedNotNull

assertDefinedNotNull<T>(value: T): asserts value is Exclude<T, null | undefined>

Ensures that the given value is not null or undefined.

Type Parameters

T

Parameters

value: T

Returns asserts value is Exclude<T, null | undefined>

Example: React Ref

function Component() {
 const ref = useRef<HTMLSpanElement>(null);
 function onClick() {
   const span = ref.current;
   assertDefinedNotNull(span);
   span.textContent = 'Hello world!';
 }

 return (
   <div>
     <button onClick={onClick}>Click me</button>
     <span ref={ref}></span>
   </div>
 )
}