Having issues building a simple JavaScript Quiz

Question

guys!

I am trying to build a basic quiz application using JavaScript and I came across a little "bump"

Why doesn't my code store an element of the allQuestions array in the currentQuestion variable ?

This is the code:

var allQuestions = [
            {question: 'What is the first letter of the alphabet?',
             choices: ['a', 'b', 'c', 'd'],
             correctAnswer: 0
            },
            {
             question: 'What is the second letter of the alphabet?',
             choices: ['a', 'b', 'c', 'd'],
             correctAnswer: 1    
            },
            {
             question: 'What is the third letter of the alphabet?',
             choices: ['a', 'b', 'c', 'd'],
             correctAnswer: 2    
            },
            {
             question: 'What is the last letter of the alphabet?',
             choices: ['a', 'b', 'c', 'z'],
             correctAnswer: 3    
            }];

var currentQuestion = {};

function pickRandomQuestion(arr) {
    return this[Math.floor(Math.random() * this.length)];
}

currentQuestion = pickRandomQuestion(allQuestions);

Thank you!

CodingIntrigue · Accepted Answer · 2013-08-13 07:26:42Z

3

You are querying this, which would be the parent context - presumably a window since I can't see a parent function. You need to look up against arr instead:

function pickRandomQuestion(arr) {
    return arr[Math.floor(Math.random() * arr.length)];
}

answered Aug 13, 2013 at 7:26

CodingIntrigue

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Comments

Quentin · Accepted Answer · 2013-08-13 07:26:50Z

0

Since you call pickRandomQuestion and not something.pickRandomQuestion, the value of this inside it is window.

Replace this with allQuestions

answered Aug 13, 2013 at 7:26

Quentin

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3 Comments

vladzam Over a year ago

Since I am passing the arr argument to the function, doesn't [this] refer to [arr] ?

CodingIntrigue Over a year ago

@shinpou No, this always refers to the context, that's why parameters need to be declared in the first place

Quentin Over a year ago

@shinpou — No, that would be arr or arguments[0]

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