Why is the presence of event checked?

Question

JavaScript

function handleClick(event){
event && event.preventDefault();
// ......
}
In what situations can event be undefined?

Answer 1

If not transferred. This is a function, anything can be inside event, like undefined, for example

handleClick(); //вызвали, но не передали, а можно и передать undefined на самом деле
function handleClick(event){
console.log(event); //undefined
}