let Declaration
JS · Variables & Constantslet variableName = value;let score = 0;
score = 10;
console.log(score);10Note Block-scoped. Cannot be re-declared in the same scope. Preferred for values that change.
Let vs var
2 snippets in JavaScript
Also written as var vs let
JSJavaScript
var Declaration (Legacy)
JS · Variables & Constantsvar variableName = value;function demo() {
if (true) {
var leaked = "visible outside block";
}
console.log(leaked);
}
demo();"visible outside block"Note Function-scoped, not block-scoped. Hoisted to the top of the function. Avoid in modern code -- use let or const instead.
Frequently asked questions
- How does JavaScript handle let vs var?
- JavaScript covers this with 2 copy-ready snippets on this page. The "let Declaration" snippet in JavaScript uses `let variableName = value;`.
- Which code does the JavaScript example use?
- The "let Declaration" snippet uses `let variableName = value;`, from the Variables & Constants section of the JavaScript cheat sheet.
- What other JavaScript snippets are shown for "let vs var"?
- Besides "let Declaration", this page also shows "var Declaration (Legacy)".
- Is there anything to watch out for?
- Yes. For "let Declaration": Block-scoped. Cannot be re-declared in the same scope. Preferred for values that change.