Where variables are visible.
✍️ 3 exercises + code challenge in this lessonScope decides where a variable can be used.
let and const inside { } are visible only in that block.Function declarations are "hoisted", so they can be called before they appear in the code. let and const cannot be used before their declaration (the "temporal dead zone").
Mastering JavaScript Scope & Hoisting helps you write clean and reliable JavaScript code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
<pre id="out"></pre>
<script>
const log = (...a) => document.getElementById("out").textContent += a.join(" ") + "\n";
const site = "CodesInTech"; // global
function show() {
const inside = "function scope";
log(site, "|", inside);
}
show();
if (true) {
let blockVar = "block scope";
log(blockVar);
}
log(typeof blockVar); // undefined outside the block
log(hoisted()); // works: declarations are hoisted
function hoisted() { return "I was called before my definition"; }
</script>Check what you learned in “JavaScript Scope & Hoisting”.
Declare a block-scoped variable.
if (true) {
x = 5;
}
Can a let variable declared inside { } be used outside the block?
Inside the function, create a local variable message = "local" and log it.
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