freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/local-scope-and-functions.english.md

id, title, challengeType

id	title	challengeType
56533eb9ac21ba0edf2244bf	Local Scope and Functions	1

Description

Variables which are declared within a function, as well as the function parameters have local scope. That means, they are only visible within that function. Here is a function myTest with a local variable called loc.

function myTest() {
  var loc = "foo";
  console.log(loc);
}
myTest(); // logs "foo"
console.log(loc); // loc is not defined

loc is not defined outside of the function.

Instructions

Declare a local variable myVar inside myLocalScope. Run the tests and then follow the instructions commented out in the editor. Hint
Refreshing the page may help if you get stuck.

Tests

tests:
  - text: No global <code>myVar</code> variable
    testString: assert(typeof myVar === 'undefined', 'No global <code>myVar</code> variable');
  - text: Add a local <code>myVar</code> variable
    testString: assert(/function\s+myLocalScope\s*\(\s*\)\s*\{\s[\s\S]+\s*var\s*myVar\s*(\s*|=[\s\S]+)\s*;[\s\S]+}/.test(code), 'Add a local <code>myVar</code> variable');

Challenge Seed

function myLocalScope() {
  'use strict'; // you shouldn't need to edit this line

  console.log(myVar);
}
myLocalScope();

// Run and check the console
// myVar is not defined outside of myLocalScope
console.log(myVar);

// Now remove the console log line to pass the test

Before Test

var logOutput = "";
var originalConsole = console
function capture() {
  var nativeLog = console.log;
  console.log = function (message) {
    logOutput = message;
    if(nativeLog.apply) {
      nativeLog.apply(originalConsole, arguments);
    } else {
      var nativeMsg = Array.prototype.slice.apply(arguments).join(' ');
      nativeLog(nativeMsg);
    }
  };
}

function uncapture() {
  console.log = originalConsole.log;
}

After Test

typeof myLocalScope === 'function' && (capture(), myLocalScope(), uncapture());
(function() { return logOutput || "console.log never called"; })();

Solution

function myLocalScope() {
  'use strict';

  var myVar;
  console.log(myVar);
}
myLocalScope();