Question

我的控制器内部有以下逻辑：

public function showvlans()
{
    $vlans=$this->switches_model->show_known_vlans($this->uri->segment(5), $this->uri->segment(4));
    //filter out VLAN 1 if its included in the list. 
    $key = array_search('1', $vlans);
    unset($vlans[$key]);
    header ('Content-Type: application/json; charset=UTF-8');
    echo json_encode($vlans);  

} // end showvlans

出于某种原因，在我从数组中过滤掉一条记录后，循环json数据的逻辑不再有效。

这是循环json数据的逻辑：

alert(returnDataFromController.length);
//loop through results
for(i = 0; i < returnDataFromController.length; i++) {
    alert(returnDataFromController[i].VlanId);
    htmlstring = htmlstring +  "<tr><td><a href=>"+returnDataFromController[i].VlanId+"</a></td><td>"+ returnDataFromController[i].Name+"</td></tr>";                         
}

线索：

警报说“未定义”。
我还在从数组中删除记录之前和之后转储了数据，这里是json数据的样子：

在删除记录之前：

[09:36:52.986] [
    {VlanId:"1", Name:"VLAN1", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"3", Name:"VLAN3", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"8", Name:"VLAN8", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"16", Name:"VLAN16", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"20", Name:"VLAN20", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"33", Name:"VLAN33", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"64", Name:"VLAN64", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"65", Name:"VLAN65", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"66", Name:"VLAN66", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"80", Name:"VLAN80", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"96", Name:"VLAN96", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"101", Name:"VLAN101", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"128", Name:"VLAN128", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"131", Name:"VLAN131", Status:"Port-based", Voice:"No", Jumbo:"No"},
    {VlanId:"417", Name:"VLAN417", Status:"Port-based", Voice:"No", Jumbo:"No"}]

AFTER：

[09:34:41.797] (
    {1:{VlanId:"3", Name:"VLAN3", Status:"Port-based", Voice:"No", Jumbo:"No"},
     2:{VlanId:"8", Name:"VLAN8", Status:"Port-based", Voice:"No", Jumbo:"No"},
     3:{VlanId:"16", Name:"VLAN16", Status:"Port-based", Voice:"No", Jumbo:"No"},
     4:{VlanId:"20", Name:"VLAN20", Status:"Port-based", Voice:"No", Jumbo:"No"},
     5:{VlanId:"33", Name:"VLAN33", Status:"Port-based", Voice:"No", Jumbo:"No"},
     6:{VlanId:"64", Name:"VLAN64", Status:"Port-based", Voice:"No", Jumbo:"No"},
     7:{VlanId:"65", Name:"VLAN65", Status:"Port-based", Voice:"No", Jumbo:"No"},
     8:{VlanId:"66", Name:"VLAN66", Status:"Port-based", Voice:"No", Jumbo:"No"},
     9:{VlanId:"80", Name:"VLAN80", Status:"Port-based", Voice:"No", Jumbo:"No"},
     10:{VlanId:"96", Name:"VLAN96", Status:"Port-based", Voice:"No", Jumbo:"No"},
     11:{VlanId:"101", Name:"VLAN101", Status:"Port-based", Voice:"No", Jumbo:"No"},
     12:{VlanId:"128", Name:"VLAN128", Status:"Port-based", Voice:"No", Jumbo:"No"},
     13:{VlanId:"131", Name:"VLAN131", Status:"Port-based", Voice:"No", Jumbo:"No"},
     14:{VlanId:"417", Name:"VLAN417", Status:"Port-based", Voice:"No", Jumbo:"No"}})

正如您所看到的，它看起来略有不同。在我使用unset之前我有一个开头[，而在我(之后。我尝试更改循环控件，以便变量i从1开始，而不是......但这也不起作用。

例如，我尝试了以下内容：

for(i = 1; i < returnDataFromController.length; i++) {

而不是

for(i = 0; i < returnDataFromController.length; i++) {

Answer 1

假设您的阵列以5个项目开头。当所有5个项目都存在时，数组键为：0,1,2,3,4

json_encode将其正确检测为枚举数组，并将其转换为JSON数组。

但是，假设你删除索引2处的项目。现在，你有：0,1,3,4。json_encode看到一个非连续的键编号，现在假设它是一个关联数组，所以你得到一个带有键0,1,3,4的JSON对象.JSON / Javascript中的对象没有length，所以你的代码不再有效。

诀窍是在将array_values传递给json_encode之前使用for，如果你想将它枚举为数组。

或者，您可以将JavaScript中的for (var i in returnDataFromController) { if (returnDataFromController.hasOwnProperty(i)) { /* your code here */ } }循环更改为：

array_values

虽然强烈建议通过{{1}}

将其转换为数组

Answer 2

Javascript / JSON区分对象和数组。对象是使用{ }语法的键值对，数组是使用[ ]的数字索引列表。

当json_encode PHP数组时，只有连续数字索引的数组才会被编码为JSON / Javascript 数组，否则它们将成为物体。 E.g：

array('foo', 'bar', 'baz')    -> ["foo", "bar", "baz"]
array(0 => 'foo', 2 => 'bar') -> {"0":"foo", "2":"bar"}

要确保您的数组具有连续的数字索引，请使用array_values。

取消设置数组中的项目已经破坏了迭代数据的逻辑

2 个答案: