检查数组是否为空或为空 [英] Check if array is empty or null

问题描述

我想知道如何检查jQuery中的数组是空还是空.我尝试了array.length === 0，但是没有用.它也没有引发任何错误.

I would like to know how to check if an array is empty or null in jQuery. I tried array.length === 0 but it didn't work. It did not throw any error either.

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
}

推荐答案

只要您的选择器实际上在工作，我就不会发现检查数组长度的代码有问题.那应该做你想要的.有很多方法可以使您的代码更简单，更易读.这是一个清理过的版本，其中包含有关我清理过的内容的注释.

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.

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
}

关于您在做什么和我做了什么的一些说明.

Some notes on what you were doing and what I changed.

1. $(this)始终是有效的jQuery对象，因此没有理由检查if ($(this)).它内部可能没有任何DOM对象，但是您可以根据需要使用$(this).length进行检查，但这在这里是不必要的，因为如果没有任何项目，则.each()循环将不会运行，因此$(this)您的.each()循环永远都是东西.
2. 在同一函数中多次使用$(this)效率低下.最好一次将它放入一个局部变量，然后从该局部变量中使用它.
3. 建议使用[]而不是new Array()初始化数组.
4. if (value)当value预期为字符串时，将同时保护value == null，value == undefined和value == ""，因此您不必执行if (value && (value != "")).您可以执行以下操作:if (value)检查所有三个空条件.
5. if (album_text.length === 0)会告诉您该数组是否为空，只要它是有效的，已初始化的数组(就在此处)即可.

1. $(this) is always a valid jQuery object so there's no reason to ever check if ($(this)). It may not have any DOM objects inside it, but you can check that with $(this).length if 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.
2. 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.
3. It's recommended to initialize arrays with [] rather than new Array().
4. if (value) when value is expected to be a string will both protect from value == null, value == undefined and value == "" so you don't have to do if (value && (value != "")). You can just do: if (value) to check for all three empty conditions.
5. 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).

您打算如何使用此选择器$("input[name='album_text[]']")?

What are you trying to do with this selector $("input[name='album_text[]']")?

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