README.md

Block Scope: Let vs Var

Eave very differently than var's when enclosed by curly braces.

Let variables will be confined to the braces where they were created: block scoping.

Var variables are hoisted outside of any curly braces they are in (except functions, this is a topic for later).

The example below illustrates how var & let variables are treated differently by JavaScript whenever a new block is created.

Index

• Learning Objective
• Study Snippet
• Helpful Links
• Interactive Practice
• Run-Time Sketches

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Learning Objective

A set of opening and closing curly braces create a new block scope. let variables are stuck inside of the block scope where they were declared, var variables are not.

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Study Snippet

let outer_let = 'outer let';
console.log('leaving outer scope');
{
    console.log('entering block scope');
    var inner_var = 'global var';
    let inner_let = 'inner let';
    console.log('leaving block scope');
};
console.log('re-entering outer scope');
inner_var = 'modified globally';
console.log('final state');

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Helpful Links

Let's temporal dead zone. (from step 3):

• 2ality
• FreeCodeCamp

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Run-Time Sketches

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