条件渲染在 reactjs 中的作用不统一？

Question

我过去曾使用过条件渲染，但由于某种原因，它在此处处理一个元素而不是另一个元素，尽管它们都使用相同的 JSON 措辞和相同类型的条件渲染？

JSON 数组

//Adobe组件数据

export default[
    {
        workName: 'Switch up your "Grub" Motiongraphic',
        workDescription: 'This is a motion graphic comparing the environmental and health effects of consuming animal products compared to insects as dietary source of protein.',
        workTech: ['Adobe After effects'],
        videoAddress: ['https://youtu.be/cloat51hzDY'],
        Images: []
    },

    {
        workName: 'Simplyfit concept poster',
         workDescription: 'This is a poster developed explaining the concept of Simplyfit, a fitness application developed as part of my final year project.',
        workTech: ['Adobe Illustrator'],
        videoAddress: [],
        Images: ['SFPoster.jpg'],
    },

    {
        workName: 'Switch up your "Grub" Infographic',
         workDescription: 'This is an infographic developed explaining the benefits of consuming insects as a source of protein.',
        workTech: ['Adobe Illustrator'],
        videoAddress: [],
        Images: ['insectMotiongraphic.png'],
    },

    {
        workName: 'Crunchy Nut Advert spoof',
         workDescription: 'This video was made as a comedic spoof of a Crunchy Nut advert',
        workTech: ['Adobe Premier Pro'],
        videoAddress: ['https://youtu.be/y8S2RUYrLN8'],
        Images: [],
    },

    {
        workName: 'Icons and Designs',
        workDescription: 'These are a selection of logos and icons created by me.',
        workTech: ['Adobe Premier Pro'],
        videoAddress: [],
        Images: ['Mylogo.png'],
    },
    
]

我遇到的问题是“videoAdress”和“Images”，我尝试为它们设置空值 undefined 等，但对于图像，唯一阻止它们渲染的是将值设置为 [ ] 但这不适用于仍然呈现 iframe 的 videoAdress？

反应js代码

{Data.map((Projects, index) => {
                        return <div className='Cards'>
                            <Carousel showThumbs={false} infiniteLoop={true} swipeable={false} emulateTouch={false} showStatus={false} autoPlay={slideShow} dynamicHeight={false}>
                                {Projects.Images && Projects.Images.map((Image, index) => { return <div className='image-iframeContainer'><img src={require("../assets/Port-images/Adobe/" + Image)} /></div> })}
                                {Projects.videoAddress && <div className='image-iframeContainer'><ReactPlayer url={Projects.videoAddress} muted={false} controls={false} onPlay={autoplayChange} onPause={autoplayChange} onEnded={autoplayChange} /></div>}
                            </Carousel>
                            {Projects.webAddress && <div className='webButton'><LinkIcon onClick=  { () => {window.open(Projects.webAddress);}}/></div>}
                            <h1>{Projects.workName}</h1>
                            {Projects.workTech.map((Tech, index) => { return <p className='techList'>{Tech}</p> })}
                            <div className='descriptionContainer'>
                                <p className='description'>{Projects.workDescription}</p>
                            </div>
                        </div>
                    })}

我想要的功能是仅在有存储地址的情况下才呈现图像和视频>

Answer 1

条件渲染通过将条件转换为真值来工作。例如：

Projects.Images && <Component />

等于：

!!Project.Images && <Component />

现在，如果您对空数组 [] 执行此操作，则真值为 TRUE。这意味着 <ReactPlayer /> 使用 [] 值呈现，而 <img /> 未呈现，因为 [].map() 不在空数组上运行。

要解决此问题，请改为：

{Projects.Images && Projects.Images.length > 0 && Projects.Images.map((Image, index) => {
  return <div className='image-iframeContainer'>
    <img src={require("../assets/Port-images/Adobe/" + Image)} />
  </div>
})} 

{Projects.videoAddress && Projects.videoAddress.length > 0 &&
<div className='image-iframeContainer'>
  <ReactPlayer url={Projects.videoAddress[0]} muted={false} controls={false} onPlay={autoplayChange} onPause={autoplayChange} onEnded={autoplayChange} />
</div>}

我注意到您的 videoAddress 没有使用 map() 方法，但我想这是一个错字