javascript - React - 未捕获的类型错误 : Cannot read property 'indexOf' of undefined

Question

我有以下组件:

import React, { Component } from 'react';

import Utilities from './utilities.js';

import Action from './action.jsx';
import SingleGridEl from './singleGridEl.jsx';

class Grid extends Component {

    constructor(props) {
        super(props);
        this.question;
        this.maxN = 110;
        this.array = [];

        this.state = {
            n1: false,
            n2: false,
            n3: false,
            n4: false,
            n5: false,
            n6: false,
            n7: false,
            n8: false,
            n9: false,
            n10: false,
            n11: false,
            n12: false,
            n13: false,
            n14: false,
            n15: false,
            n16: false,
            n17: false,
            n18: false,
            n19: false,
            n20: false,
            n21: false,
            n22: false,
            n23: false,
            n24: false
        }

        this.hideSingleGrid = this.hideSingleGrid.bind(this);
    }

    getRandomQuestion() {   
        let randomN = Utilities.generateRandomNumber(this.array, this.maxN);
        console.log(randomN);
        this.question = this.props.current.data.questions[randomN];
        console.log(this.question);
        return this.question;
    }

    hideSingleGrid(el, val) {
        var s = {};
        s[el] = val;
        this.setState(s);
    }

    componentWillMount() {
        this.getRandomQuestion();
    }

    render() {
        return (
            <section className="game">
                <div className="grid">

                    <div className="row">
                        <SingleGridEl visibility={this.state.n1} />
                        <SingleGridEl visibility={this.state.n2} />
                        <SingleGridEl visibility={this.state.n3} />
                        <SingleGridEl visibility={this.state.n4} />
                        <SingleGridEl visibility={this.state.n5} />
                        <SingleGridEl visibility={this.state.n6} />
                    </div>
                    <div className="row">
                        <SingleGridEl visibility={this.state.n7} />
                        <SingleGridEl visibility={this.state.n8} />
                        <SingleGridEl visibility={this.state.n9} />
                        <SingleGridEl visibility={this.state.n10} />
                        <SingleGridEl visibility={this.state.n11} />
                        <SingleGridEl visibility={this.state.n12} />
                    </div>
                    <div className="row">
                        <SingleGridEl visibility={this.state.n13} />
                        <SingleGridEl visibility={this.state.n14} />
                        <SingleGridEl visibility={this.state.n15} />
                        <SingleGridEl visibility={this.state.n16} />
                        <SingleGridEl visibility={this.state.n17} />
                        <SingleGridEl visibility={this.state.n18} />
                    </div>
                    <div className="row">
                        <SingleGridEl visibility={this.state.n19} />
                        <SingleGridEl visibility={this.state.n20} />
                        <SingleGridEl visibility={this.state.n21} />
                        <SingleGridEl visibility={this.state.n22} />
                        <SingleGridEl visibility={this.state.n23} />
                        <SingleGridEl visibility={this.state.n24} />
                    </div>
                </div>

                <Action t={this.hideSingleGrid} question={this.question} getRandomQuestion={this.getRandomQuestion.bind(this)}/>
            </section>
        );
    }
}

export default Grid;

它使用了以下实用程序方法:

var Utilities = (function (array, maxN) {

    function generateRandomNumber(array, maxN) {
        let randomN = Math.floor((Math.random() * maxN) + 1);

        if(array.indexOf(randomN) === -1) {
            array.push(randomN);
        }
        else {
            randomN = generateRandomNumber();
        }

        console.log(array);

        return randomN;
    }

    return {
        generateRandomNumber: generateRandomNumber
    };

})();

export default Utilities;

此实用程序方法生成一个随机数并将其存储在数组中，以便根据传入的最大长度返回的每个随机数都是唯一的。

action.jsx 组件使用相同的实用方法:

import React, { Component } from 'react';

import Utilities from './utilities.js';

class Action extends Component {
    constructor(props) {
        super(props);

        this.maxN = 24;
        this.array = [];

        this.state = {
            question: props.question
        }
    }

    getNewQuestion(e) {
        let answerId = "option_" + this.state.question.correct_option;

        if(e.target.getAttribute('data-question') == answerId) {
            let randomNumber = Utilities.generateRandomNumber(this.array, this.maxN);
            this.props.t('n'+randomNumber, true);
            this.setState({
                question: this.props.getRandomQuestion()
            });
        }
        else {
            console.log('wrong');
        }
    }

    render() {
        let state = this.state;

        return(
            <div className="action">
                <div className="action-question">
                    <h3>{state.question.question}</h3>
                </div>

                <div className="action-answers">
                    <p data-question="option_1" onClick={this.getNewQuestion.bind(this)}>{state.question.option_1}</p>
                    <p data-question="option_2" onClick={this.getNewQuestion.bind(this)}>{state.question.option_2}</p>
                    <p data-question="option_3" onClick={this.getNewQuestion.bind(this)}>{state.question.option_3}</p>
                    <p data-question="option_4" onClick={this.getNewQuestion.bind(this)}>{state.question.option_4}</p>
                </div>
            </div>
        );
    }
}   

export default Action;  

当我单击每个“p”时，“this.getNewQuestion”会检查我们是否单击了正确的答案，并转到具有相关答案的下一个问题。

在游戏过程中的某个时刻(非常随机)，我在控制台中收到以下错误。错误指的是实用方法:

if(array.indexOf(randomN) === -1) {

我无法弄清楚是什么导致了该错误..

Answer 1

在调用 indexOf 之前，您需要检查您的 array 参数实际上是否是一个数组:

if(Array.isArray(array) && array.indexOf(randomN) === -1) {

}

或提供默认参数

function generateRandomNumber(array = [], maxN) {

代码中的这一行正在调用不带任何参数的函数，并将触发错误:

else {
   randomN = generateRandomNumber();
}