What’s the difference between let, const and var in JavaScript?

I'm confused about when to use let, const, or var in JavaScript. They seem similar but behave differently. Can someone explain the key differences for a beginner?

Let and const are block-scoped while var is function-scoped. Var can also be redeclared, which can cause issues. Let is good for values that change. Const is for values that stay the same.

In modern JavaScript, use const by default and only use let when you really need to reassign the variable. Avoid var unless you’re maintaining old code.