TypeError：值不实现接口EventListener [英] TypeError: Value does not implement interface EventListener

问题描述

这个工程在IE和Chrome中找到，但是，在Firefox中，我得到的错误：
$ b

TypeError：Value没有实现接口EventListener。

这段代码是由php脚本发布的，所以我不得不添加if语句来确定id是否存在，首先要避免在Chrome中出错。

以下是代码：

HTML
< a id =注销>注销< / a>

JavaScript

  if（document.getElementById（Logout）！= null）{
 var Logout_Link = document.getElementById（Logout）; 
 Logout_Link.addEventListener（'click'，注销，true）; 
 
函数Logout（）{
 var just_logged_out = 1; 
 window.location.href =logout-redirect.php; 
 
 
 
 $ div $解析方案

$如果（...）{
函数...（）{
...
}
}
code>

无效。函数声明必须位于函数或程序体的顶层，位于块的内部他们的行为是依赖于实现的。把它移到if语句之外：

$ p $ function Logout（）{
var just_logged_out = 1;
window.location.href =logout-redirect.php;


if（document.getElementById（Logout）！= null）{
var Logout_Link = document.getElementById（Logout）;
Logout_Link.addEventListener（'click'，注销，true）;





$ b

所以如果函数没有被正确的声明，奇怪的错误信息是什么？你可能已经期望像错误的自变量错误：处理程序是'undefined'。但实际上不是， 注销 code>确实指向您的链接元素。这确实没有实现 EventListener 接口（JavaScript函数可以）。

This works find in IE and Chrome, however, in Firefox, I get the error:

"TypeError: Value does not implement interface EventListener."

This code is posted by a php script, so I had to add the if statement determining if the id exists, first, to avoid errors in Chrome.

Here's the code:

HTML <a id="Logout">Logout</a>

JavaScript

if (document.getElementById("Logout") != null) {
    var Logout_Link = document.getElementById("Logout");
    Logout_Link.addEventListener('click', Logout, true);

    function Logout() {            
        var just_logged_out = 1;
        window.location.href = "logout-redirect.php";
    }
}

解决方案

if (…) {
    function …() {            
        …
    }
}

is invalid. Function declarations must be on the top level of function or program bodies, inside of blocks their behaviour is implementation-dependent. Move it outside the if-statement:

function Logout() {            
    var just_logged_out = 1;
    window.location.href = "logout-redirect.php";
}

if (document.getElementById("Logout") != null) {
    var Logout_Link = document.getElementById("Logout");
    Logout_Link.addEventListener('click', Logout, true);
}

So if the function was not declared [correctly], what's that odd error message? You might've expected something like WRONG ARGUMENTS ERROR: handler is 'undefined'. But actually it's not, Logout does refer to your link element. And that does indeed not implement the EventListener interface (JavaScript functions do).

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