JSFiddle - React, Tailwind, and code Playground

JavaScript

var i;
if (i) {
    alert('True. Type of i: ' + typeof i);
} else {
    alert('False. Type of i: ' + typeof i);
}

var j = 0  // аналогично '', false, null;
if (j) {
    alert('True. Type of j: ' + typeof j);
} else {
    alert('False. Type of j: ' + typeof j);
}