来自php页面的ajax调用-检查结果是否为空数组 [英] ajax calls from php page - checking for an empty array as result
问题描述
我有一个包含以下javascript的php页面：
I have a php page which includes the following javascript:
<script>
$(document).ready(function(){
$('#search').hide();
});
$('#L1Locations').live('change',function(){
var htmlstring;
$selectedvalue = $('#L1Locations').val();
$.ajax({
url:"<?php echo site_url('switches/getbuildings/');?>" + "/" + $selectedvalue,
type:'GET',
dataType:'json',
success: function(returnDataFromController) {
alert('success');
var htmlstring;
htmlstring="<select name='L2Locations' id='L2Locations'>";
htmlstring = htmlstring + "<option value='all'>All</option>";
console.log(returnDataFromController);
var JSONdata=[returnDataFromController];
alert('string length is' + JSONdata.length);
if(JSONdata.length > 0)
{
for(var i=0;i<JSONdata.length;i++){
var obj = JSONdata[i];
for(var key in obj){
var locationkey = key;
var locationname = obj[key];
htmlstring = htmlstring + "<option value='" + locationkey + "'>" + locationname + "</option>";
}
}
$('#l2locations').html(htmlstring);
}
else
{
alert('i think undefined');
$('#l2locations').html('');
}
}
});
$('#search').show();
});
</script>
我要完成的操作是动态显示组合框，如果变量 returnDataFromController具有项目。
what i'm trying to accomplish is dynamically show a combo box if the variable "returnDataFromController" has any items.
但是我认为我在检查JSONdata.length的行中存在一个错误。
无论ajax调用是否返回填充的数组还是一个空的，长度总是显示为1。我想知道当您要求长度时该算什么。也许我的dataType属性不正确？我不确定。
But I think I have a bug with the line that checks JSONdata.length.
Regardless of whether or not the ajax call returns a populated array or an empty one, the length always shows a being 1. I think I'm confused as to what is counted when you ask for the length. Or maybe my dataType property is incorrect? I'm not sure.
以防万一，当我确实从ajax调用中获取数据时， console.log（returnDataFromController）行给出以下结果（因此当应当创建组合）
In case it helps you, the "console.log(returnDataFromController)" line gives the following results when i do get data back from the ajax call (and hence when the combo should be created)
[16:28:09.904] ({'2.5':"Admin1", '2.10':"Admin2"}) @ http://myserver/myapp/index.php/mycontroller/getbranches:98
在这种情况下，组合框将显示正确的内容。
In this scenario the combo box is displayed with the correct contents.
但是在返回空数组的情况下，也会创建组合框。这是console.log调用转储的内容：
But in scenario where I'm returning an empty array, the combo box is also created. Here's what the console.log call dumps out:
[16:26:23.422] [] @ http://myserver/myapp/index.php/mycontroller/getbranches:98
你能告诉我我要去哪里了吗？
Can you tell me where I'm going wrong?
编辑：
我意识到我将返回数据视为一个对象-我想这就是我想要的，因为我要返回一个数组。
我想我需要知道如何正确检查JavaScript中数组的长度。我以为只是长度。
I realize that I'm treating my return data as an object - I think that's what I want because i'm getting back an array. I guess I need to know how to properly check the length of an array in javascript. I thought it was just .length.
谢谢。
编辑2：
也许我应该改变控制器发送的结果？我应该返回false或NULL而不是返回空数组？
EDIT 2 : Maybe I should just chagne the results my controller sends? Instead of returning an empty array, should I return false or NULL?
if (isset($buildingforbranch))
{
echo json_encode($buildingforbranch);
}
else
{
echo json_encode(false);
}
编辑3：
基于位于在JavaScript中解析JSON的帖子？ ，我将ajax调用的成功部分中的代码更改为：
Based on the post found at Parse JSON in JavaScript?, I've changed the code in the "success" section of the ajax call to look like:
success: function(returnDataFromController) {
var htmlstring;
htmlstring="<select name='L2Locations' id='L2Locations'>";
htmlstring = htmlstring + "<option value='all'>All</option>";
console.log(returnDataFromController);
var JSONdata=returnDataFromController,
obj = JSON && JSON.parse(JSONdata) || $.parseJSON(JSONdata);
alert(obj);
}
但是我在
[18:34:52.826] SyntaxError: JSON.parse: unexpected character @ http://myserver/myapp/index.php/controller/getbranches:102
第102行是：
obj = JSON && JSON.parse(JSONdata) || $.parseJSON(JSONdata);
推荐答案
问题是来自控制器的数据格式错误JSON。
The problem was that the data from the controller is malformed JSON.
请注意我的帖子中显示返回数据的部分：
Note the part of my post where I show the return data:
({'2.5':"Admin1", '2.10':"Admin2"})
2.5应该用双引号而不是单引号。
我不知道这种情况如何/为什么发生，但我将创建另一篇文章来处理该问题。感谢大家。
The 2.5 should be in double quotes not single quotes. I don't understand how / why this is happening but I will create another post to deal with that question. Thanks everyone.
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