通过使用 Object.entries() 指示某个元素是否存在答案

【问题标题】：Indicate if a certain element exists through the use of Object.entries ()通过使用 Object.entries() 指示某个元素是否存在
【发布时间】：2022-01-10 16:36:15
【问题描述】：

我需要你的帮助；我有一个对象数组（称为 bookArr，如下所示），如下所示。

bookArr 是：

[
  {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
  {part: 'Author', value: 'Andrzej Sapkowski', id: 2},
  {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
  {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
]

有时，例如，作者不知名；所以一旦我为每个部分做了一个循环，我想知道作者（总是考虑到部分）是否丢失，因为我在 if 条件下需要它。

所以我做了如下：

if (Object.entries(results)[x][1].part == "Author") {
  document.getElementById("auth").innerHTML = Object.entries(results)[x][1].value;
} else if (Object.entries(results)[x][1].part == "") {
  do this....
}

我尝试使用Object.entries(results)[x][1].part == ""，但它不起作用。

我该如何解决我的问题？

编辑

如果缺少Author，则缺少Author对应的整行，因此不存在

{1: {…}, 2: {…}, 3: {…}, 4: {…}}
    1: {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
    2: {part: 'Author', value: 'Andrzej Sapkowski', id: 2},
    3:{part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
    4: {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
    [[Prototype]]: Object

完整代码：（正如我所说，作者并不总是存在于数组中（因此最后一条指令源自它））

while (x < Object.entries(results).length) {
    if (Object.entries(results)[x][1].part == "Title"){
        document.getElementById("title").innerHTML = Object.entries(results)[x][1].value;
        
    }
    else if (Object.entries(results)[x][1].part == "Text"){
        document.getElementById("txt1").innerHTML = Object.entries(results)[x][1].value;
    }
    else if (Object.entries(results)[x][1].part == "Image"){
        document.getElementById("img").src = Object.entries(results)[x][1].value;
    }
    else if (Object.entries(results)[x][1].part == "Author"){
        document.getElementById("auth").innerHTML = Object.entries(results)[x][1].value;;
    }
    else if(!Object.entries(results)[x][1].some(item => item.part == 'Author')) {
      console.log('yes')
      document.getElementById("auth").style.display="none";
    }
    
x++;
}

【问题讨论】：

欢迎来到 Stack Overflow！如果您还没有，请使用tour（您将获得徽章！），四处看看，并通读help center，尤其是How do I ask a good question? 我还推荐Jon Skeet 的Writing the Perfect Question 和Question Checklist .
恐怕问题中的信息太零碎，我们无法提供帮助。您谈论的是数组，但随后您使用的是Object.entries，它适用于非数组对象（尽管它适用于数组，因为数组也是对象）。请使用 minimal reproducible example 来更新您的问题，以展示问题，最好是使用 Stack Snippets（[<>] 工具栏按钮）的 runnable 问题； here's how to do one.
@T.J.Crowder 对象数组
我知道，但同样，你不会使用Object.entries。我们需要更多的上下文。你是按条目做的吗？还是整个阵列只用一次？还是……？
为什么会这样？与其他字段一起正常工作。我不明白为什么 Object.entries (results) [x] [1] .part == "" (just put "") 不起作用

标签： javascript loops

【解决方案1】：

如果您只想检查数组是否包含part:Author，只需使用Array.find()，您无需运行循环。

更新：未定义 x 并使用 Object.entries(results)[1] 代替 Object.entries(results)[x][1]

//No author
let results = [
 {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
  {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
  {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
]

function check(){
let x = 0
if(!Object.entries(results)[1].find(item => item.part == 'Author')) {
console.log('no author')
      document.getElementById("idframe").style.display="none";
    }
while (x < Object.entries(results).length) {
    if (Object.entries(results)[x][1].part == "Title"){
        document.getElementById("title").innerHTML = Object.entries(results)[x][1].value;
        
    }
    else if (Object.entries(results)[x][1].part == "Text"){
        document.getElementById("txt1").innerHTML += Object.entries(results)[x][1].value;
    }
    else if (Object.entries(results)[x][1].part == "Image"){
        document.getElementById("img").src += Object.entries(results)[x][1].value;
    }
    else if (Object.entries(results)[x][1].part == "Author"){
        document.getElementById("auth").innerHTML += Object.entries(results)[x][1].value; 
        console.log(' have author')
    }
    
x++;
}
}
check()


//Without author

<div id=img></div>
<div id=title></div>
<div id=txt1></div>
<div id=auth></div>
<div id=idframe></div>

【讨论】：

我再告诉你一件事。如果一本书有作者，则两篇文章都会显示在控制台上。这样 if 语句总是被读取
@a_l_e_x，不，这不是真实的声明，请再次检查。它使auth 被显示：无
是的，我明白你的意思。但不幸的是，该程序似乎这样做了。没有什么办法可以解决这个问题了？
@a_l_e_x，我想是的，我们已经讨论了 30 多行大声笑，我认为它应该是绝对有效的（在我这边工作）。我尽力了：（不知道为什么不为你工作......这是我第一次花这么多时间与人们谈论特定主题。哈哈。希望我的回答在某些情况下对你有所帮助！
完美，无限感谢。只要我有机会投票给答案，我就会这样做，因为您非常乐于助人和慷慨。我永远不会停止感谢你。感谢您的耐心等待。

【解决方案2】：

如果我假设数组只代表一本书，并且您想知道value 是否对于part: "Author" 元素是空白的或者没有这样的元素，那么Object.entries 在这里没有任何作用。相反，使用find 来查找是否存在带有part: "Author" 的元素，如果存在，则检查该元素以查看它是否具有非空白value：

const authorElement = bookArr.find(({part}) => part === "Author");
if (!authorElement) {
    // There is no `part: "Author"` element at all
} else if (!authorElement.value) {
    // There is a `part: "Author"` element, but `value` is missing or blank
} else {
    // There's a `part: "Author"` element and it has a non-blank `value`
}

现场示例：

function check(label, array) {
    const authorElement = array.find(({part}) => part === "Author");
    if (!authorElement) {
        // There is no `part: "Author"` element at all
        console.log(label, "no Author part");
    } else if (!authorElement.value) {
        // There is a `part: "Author"` element, but `value` is missing or blank
        console.log(label, "Author part has missing or blank value");
    } else {
        // There's a `part: "Author"` element and it has a non-blank `value`
        console.log(label, `Author part has value "${authorElement.value}"`);
    }
}

const bookArr = [
    {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
    {part: 'Author', value: 'Andrzej Sapkowski', id: 2},
    {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
    {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
];
check("bookArr (array from the question):", bookArr);

const arrayWithoutElement = [
    {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
    {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
    {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
];
check("arrayWithoutElement:", arrayWithoutElement);

const arrayWithMissingValue = [
    {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
    {part: 'Author', id: 2},
    {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
    {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
];
check("arrayWithMissingValue:", arrayWithMissingValue);

const arrayWithBlankValue = [
    {part: 'Text', value: 'Geralt is a witcher, a stronger and more resilient individual than any human, who earns his living by killing those creatures that dismay even the most daring: demons, orcs, evil elves.' , id: 1},
    {part: 'Author', value: '', id: 2},
    {part: 'Image', value: 'book_imgrt5432tp.jpg', id: 3},
    {part: 'Title', value: "The guardian of the innocents. The Witcher. Vol. 1", id: 4}
];
check("arrayWithMissingValue:", arrayWithBlankValue);

【讨论】：