jQuery 检查数组是否为空或空
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Check if array is empty or null
提问by input
I would like to know how to check if an array is empty or null in jQuery. I tried array.length === 0but it didn't work. It did not throw any error either.
我想知道如何在 jQuery 中检查数组是空的还是空的。我试过了，array.length === 0但没有用。它也没有抛出任何错误。
This is the code:
这是代码：
var album_text = new Array();
$("input[name='album_text[]']").each(function(){
if( $(this).val() && $(this).val() != '') {
album_text.push($(this).val());
}
});
if (album_text.length === 0) {
$('#error_message').html("Error");
}
else {
// send data
}
回答by jfriend00
As long as your selector is actually working, I see nothing wrong with your code that checks the length of the array. That should do what you want. There are a lot of ways to clean up your code to be simpler and more readable. Here's a cleaned up version with notes about what I cleaned up.
只要您的选择器实际工作，我认为您检查数组长度的代码没有任何问题。那应该做你想做的。有很多方法可以清理您的代码，使其更简单、更具可读性。这是一个清理版本，其中包含有关我清理内容的注释。
var album_text = [];
$("input[name='album_text[]']").each(function() {
var value = $(this).val();
if (value) {
album_text.push(value);
}
});
if (album_text.length === 0) {
$('#error_message').html("Error");
}
else {
//send data
}
Some notes on what you were doing and what I changed.
关于你在做什么和我改变了什么的一些笔记。
$(this)is always a valid jQuery object so there's no reason to ever checkif ($(this)). It may not have any DOM objects inside it, but you can check that with$(this).lengthif you need to, but that is not necessary here because the.each()loop wouldn't run if there were no items so$(this)inside your.each()loop will always be something.- It's inefficient to use $(this) multiple times in the same function. Much better to get it once into a local variable and then use it from that local variable.
- It's recommended to initialize arrays with
[]rather thannew Array(). if (value)when value is expected to be a string will both protect fromvalue == null,value == undefinedandvalue == ""so you don't have to doif (value && (value != "")). You can just do:if (value)to check for all three empty conditions.if (album_text.length === 0)will tell you if the array is empty as long as it is a valid, initialized array (which it is here).
$(this)始终是有效的 jQuery 对象，因此没有理由检查if ($(this)). 它里面可能没有任何 DOM 对象，但是$(this).length如果需要，您可以检查它，但这在这里不是必需的，因为.each()如果没有项目，循环将不会运行，因此$(this)您的.each()循环内部将始终存在。- 在同一个函数中多次使用 $(this) 是低效的。最好将它放入一个局部变量，然后从该局部变量中使用它。
- 建议使用
[]而不是初始化数组new Array()。 if (value)当值预计将是一个字符串将两者保护value == null，value == undefined而且value == ""这样你就不必做if (value && (value != ""))。您可以这样做：if (value)检查所有三个空条件。if (album_text.length === 0)只要它是一个有效的初始化数组（它在这里），就会告诉你数组是否为空。
What are you trying to do with this selector $("input[name='album_text[]']")?
你想用这个选择器做$("input[name='album_text[]']")什么？
回答by Mayank Raipure
User JQuery is EmptyObject to check whether array is contains elements or not.
用户 JQuery 是 EmptyObject 来检查数组是否包含元素。
var testArray=[1,2,3,4,5];
var testArray1=[];
console.log(jQuery.isEmptyObject(testArray)); //false
console.log(jQuery.isEmptyObject(testArray1)); //true
回答by Daniel A. White
You should check for ''(empty string) before pushing into your array. Your array has elements that are empty strings. Then your album_text.length === 0will work just fine.
''在推入数组之前，您应该检查（空字符串）。您的数组具有为空字符串的元素。那么你的album_text.length === 0将工作得很好。
回答by rhinoxi
I think it is dangerous to use $.isEmptyObject from jquery to check whether the array is empty, as @jesenko mentioned. I just met that problem.
正如@jesenko 提到的，我认为使用 jquery 中的 $.isEmptyObject 来检查数组是否为空是危险的。我刚遇到那个问题。
In the isEmptyObject doc, it mentions:
在isEmptyObject 文档中，它提到：
The argument should always be a plain JavaScript Object
参数应该总是一个普通的 JavaScript 对象
which you can determine by $.isPlainObject. The return of $.isPlainObject([])is false.
您可以通过 确定$.isPlainObject。的返回$.isPlainObject([])是假的。
