Thinking about scope (for Sara)

example1.js

'use strict';

var outerFunction, innerFunction;

outerFunction = function() {
  innerFunction = function() {
    console.log('inner');
  };
  console.log('outer');
};

outerFunction();
innerFunction();

example2.js

'use strict';

function outerFunction() {
  console.log('outer');
  function innerFunction() {
    console.log('inner');
  }
}

outerFunction();
innerFunction();

example3.js

'use strict';

function outerFunction() {
  var mySecretValue = 42;
  return mySecretValue;
}

var secret = outerFunction();
console.log(secret);

example4.js

'use strict';

var secretKeeper, secret;

function outerFunction() {
  var mySecretValue = 42;
  return function() {
    return mySecretValue;
  };
}

secretKeeper = outerFunction();
secret = secretKeeper();
console.log(secret);

example5.js

'use strict';

var secretKeeper, secret;

function outerFunction() {
  var mySecretValue = 42;
  return function() {
    mySecretValue++;
    return mySecretValue;
  };
}

secretKeeper = outerFunction();
console.log(secretKeeper());
console.log(secretKeeper());

Thinking-points.md

(You should be able to clone this gist and run node example[x].js for each JS file here to do the exercises).

• What do you think will happen when you execute example1.js?
• What happens if you comment out line 12 and run example1.js? Why?
• What do think will happen when you execute example2.js? Did it work as you expected?
• What would happen if you added a new line to the end of example3.js and console.log(mySecretValue);? Why?
• What type is secretKeeper on line 12 of example4.js? How did it get assigned?
• What code does secretKeeper() execute when it is invoked on line 13 of example4.js? What does it return and how?
• What type is secret as of line 13 of example4.js?
• What will log to the console in line 14 of example5.js? Line 15?
• What is the lifecycle of mySecretValue in example5.js? How and when does it change value?