有问题构建一个简单的JavaScript测验

Question

人！

我正在尝试使用JavaScript构建一个基本的测验应用程序，但我遇到了一些“碰撞”

为什么我的代码不在currentQuestion变量中存储allQuestions数组的元素？

这是代码：

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);

谢谢！

Answer 1

您正在查询this，这将是父上下文 - 可能是window，因为我看不到父function。您需要反对arr：

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

Answer 2

由于您致电pickRandomQuestion而非something.pickRandomQuestion，其中this的值为window。

将this替换为allQuestions