variable scope example

example.js

// For the purposes of this demo, hard-code answer and response
let answer = 4;
let response = 'e';


// THE FOLLOWING WILL *NOT* WORK
for (let i = 0; i < 3; i++) {

    if (answer % 2 == 0 && response == 'e') {
        let correct = true;
    } else if (answer % 2 == 1 && response == '0') {
        let correct = true;
    } else {
        let correct = false;
    }

    // Initializing `correct` within the if/else if/else block makes it only available 
    // within that block. Thus, when we try to access it in the following line, we get 
    // the error Uncaught ReferenceError: correct is not defined
    console.log(correct);
}

// THE FOLLOWING WILL WORK
for (let i = 0; i < 3; i++) {

    // To fix, we initialize correct as null *before* the if/else if/else block
    let correct = null;

    if (answer % 2 == 0 && response == 'e') {
        correct = true;
    } else if (answer % 2 == 1 && response == '0') {
        correct = true;
    } else {
        correct = false;
    }

    // This now works
    console.log(correct);
}