JSFiddle - React, Tailwind, and code Playground

JavaScript

var a = 1;

function b() {
    console.log(a); // undefined
    var a = 2;
}

console.log("At b:");
b();

console.log("At catch:");
try {
    console.log(x); // ReferenceError
} catch(ex) {
    console.log(a); // 1, not undefined
    var a = 3;
}