Question

我想使用基于ReactJS中条件的map函数从数组中获得一个索引值。

当前，如果条件通过，我将获得所有索引值，但是一旦条件为真，我想停止该条件。这样我在返回时将索引一个...

JSON对象：

question: [

    {
        'question_type': 'TEXT',
        'question': 'how long have the founders known each other?',
        'question_status': 'Done',
        'expectedAnswer': "",
        'answer': '5 yrs'
    },
    {
        'question_type': 'EITHER',
        'question': 'does any founder have an exit?',
        'question_status': 'Pending',
        'expectedAnswer':['Yes','No'],
        'answer': "",
    },
    {
        'question_type': 'DROPDOWN',
        'question': 'Where are you from?',
        'question_status': 'Pending',
        'expectedAnswer':['india','USA','UK'],
        'answer': "",
    },
]

执行过滤的功能

const currentQuestion = question.map(function (data, i) {
            if (data.question_status === 'Pending') {
                return (
                    <Row key={i} className='chat-box'>
                        <Col xl='1' lg='1' md='1' className="question-image">
                            <img src='images/chatbot/rectangle-26.png' />
                        </Col>
                        <Col xl='11' lg='11' md='11' className="question-text">
                            {data.question}
                        </Col>

                        <Col xl="11" lg="11" md="11" className="answer-box ">
                            {/* <img className="answer-image pull-right" src='images/chatbot/group-9.png' /> */}
                            <div className="pull-right custome-radio">
                                {data.question_type === 'EITHER'? this.renderEitherField(data.expectedAnswer):null} 
                            </div>
                        </Col>
                    </Row>
                );
            }

        }.bind(this));

预期输出：

{
    'question_type': 'EITHER',
    'question': 'does any founder have an exit?',
    'question_status': 'Pending',
    'expectedAnswer':['Yes','No'],
    'answer': "",

}

我只想过滤第一个索引值，而不是第一个和第二个。目前，我正在获取第一和第二索引值，因为两个question_status均为“ Pending”，但是在这里我只想获取第一索引值（一旦第一次出现，它必须停止返回值）

如果这不是最好的方法，请告诉我。...

Answer 1

您可以使用Array.find方法。它从满足条件的数组中返回第一个值，否则未定义。

const data = [

                {
                    'question_type': 'TEXT',
                    'question': 'how long have the founders known each other?',
                    'question_status': 'Done',
                    'expectedAnswer': "",
                    'answer': '5 yrs'
                },
                {
                    'question_type': 'EITHER',
                    'question': 'does any founder have an exit?',
                    'question_status': 'Pending',
                    'expectedAnswer':['Yes','No'],
                    'answer': "",
                },
                {
                    'question_type': 'DROPDOWN',
                    'question': 'Where are you from?',
                    'question_status': 'Pending',
                    'expectedAnswer':['india','USA','UK'],
                    'answer': "",
                },
            ]
const out = data.find(x => x.question_status === 'Pending')

console.log(out)

Please keep in mind that Array.find is not supported on IE. You need to use a Polyfill.

另一种方法可以是返回已过滤数组的第0个索引。如果存在，它将返回未定义的值。

Answer 2

您可以使用for循环。

let arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
for (let a of arr) {
  console.log(a);
  if (a === 5) {
    break;
  }
}

您可以将此示例用作满足您条件的参考。

Answer 3

您可以使用filter函数来使用question_status功能来过滤出结果

const question = [

    {
        'question_type': 'TEXT',
        'question': 'how long have the founders known each other?',
        'question_status': 'Done',
        'expectedAnswer': "",
        'answer': '5 yrs'
    },
    {
        'question_type': 'EITHER',
        'question': 'does any founder have an exit?',
        'question_status': 'Pending',
        'expectedAnswer':['Yes','No'],
        'answer': "",
    },
    {
        'question_type': 'DROPDOWN',
        'question': 'Where are you from?',
        'question_status': 'Pending',
        'expectedAnswer':['india','USA','UK'],
        'answer': "",
    },
]
const arr = question.filter(q => q.question_status === 'Pending')

console.log(arr);

在上面的代码中，输出将如下所示，

[ { question_type: 'EITHER',
    question: 'does any founder have an exit?',
    question_status: 'Pending',
    expectedAnswer: [ 'Yes', 'No' ],
    answer: '' },
  { question_type: 'DROPDOWN',
    question: 'Where are you from?',
    question_status: 'Pending',
    expectedAnswer: [ 'india', 'USA', 'UK' ],
    answer: '' } ]

因此您可以简单地从输出中获取第一个元素。

Answer 4

使用for语句满足您的需求

const data = [

                {
                    'question_type': 'TEXT',
                    'question': 'how long have the founders known each other?',
                    'question_status': 'Done',
                    'expectedAnswer': "",
                    'answer': '5 yrs'
                },
                {
                    'question_type': 'EITHER',
                    'question': 'does any founder have an exit?',
                    'question_status': 'Pending',
                    'expectedAnswer':['Yes','No'],
                    'answer': "",
                },
                {
                    'question_type': 'DROPDOWN',
                    'question': 'Where are you from?',
                    'question_status': 'Pending',
                    'expectedAnswer':['india','USA','UK'],
                    'answer': "",
                },
            ]

function currentQuestion() {
   for (var i=0; i<data.length; i++) {
       if (data[i].question_status === "Pending") return data[i];
   }
}

条件满足后，这里的for语句将消失，该函数将为您提供所需的值

使用map函数根据条件返回一个数组对象，而不是所有对象

4 个答案: