Tip 3: Isolate Information with Block Scoped Variables
Explore how to use block scoped variables with let to avoid common JavaScript scoping issues in loops. Understand the difference between var and let, and learn how let locks variable values during each loop iteration for clearer, more predictable code.
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At one point or another, every developer will make the mistake of capturing
the wrong variable during a for loop. The traditional solution involves some
pretty advanced JavaScript concepts. Fortunately, the let variable declaration
makes this complex issue disappear.
Block scoped variables
Remember, when you use a block-scoped variable declaration, you’re creating
a variable that’s only accessible in the block. A variable declared in an if block
isn’t available outside the curly braces. A variable declared inside a for loop
isn’t available outside the curly braces of the for loop. But that doesn’t mean
you can’t access variables declared outside a function. If you declare a block
scope variable at the top of a function, it is accessible inside the block.
Lexically scoped variables
If you declare a lexically scoped variable, ...