let and const have two broad differences from var: They are block scoped. Accessing a var before it is declared has the result undefined; accessing a let or const before it is declared throws ReferenceError: console.log(aVar); // undefined console.log(aLet); // Causes ReferenceError: Cannot access ‘aLet’ before initialization var aVar = 1; let aLet = 2; … Read more
Do let statements create properties on the global object? According to the spec, no: A global environment record is logically a single record but it is specified as a composite encapsulating an object environment record and a declarative environment record. The object environment record has as its base object the global object of the associated … Read more
@thefourtheye is correct in saying that these variables cannot be accessed before they are declared. However, it’s a bit more complicated than that. Are variables declared with let or const not hoisted? What is really going on here? All declarations (var, let, const, function, function*, class) are “hoisted” in JavaScript. This means that if a … Read more
What’s the difference between using “let” and “var”?