freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/es6/compare-scopes-of-the-var-and-let-keywords/index.md

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Compare Scopes of the var and let Keywords

Compare Scopes of the var and let Keywords

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Problem Explanation

Change the code so that the variable i declared in the if block is separately scoped than the variable i declared at the beginning of the function.

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Hints

Hint 1

• Be certain not to use the var keyword anywhere in your code.

Hint 2

• Remember that let's scope is limited to the block, function or statement in which you declare it.

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Solutions

Solution 1 (Click to Show/Hide)

function checkScope() {
  "use strict";
  let i = "function scope";
  if (true) {
    let i = "block scope";
    console.log("Block scope i is: ", i);
  }
  console.log("Function scope i is: ", i);
  return i;
}

Code Explanation

By using let you can declare variables in relation to their scope.

Relevant Links

• "let" - MDN Javascript reference
• Rauschmayer, Axel. "Variables and scoping in ECMAScript 6". 2ality.com, 2015-02-07. Accessed 11 Dec 2018.
• Bos, Wes. "Quick Tip: Use let with for Loops in JavaScript". wesbos.com, 16 Aug 2016. Accessed 11 Dec 2018.