Javascript – Check if an element has event listener on it. No jQuery

javascript

How to check if an element has event listener on it, if I use an inline function on it like the code below? Because I have a function that recalls the function and add the event listener, but it cause to have duplication event listener causing it to trigger a function twice. How can I check it so I can prevent it to add an event listener if is it already exist? 

for (var a = 0;a<formFieldInput.length;a++) {
    if(formFieldInput[a].hasAttribute("name") && formFieldInput[a].attributes.title.value !== "Valid Until") {
        formFieldInput[a].addEventListener("click",function(event) {
            toggleFieldList(event,"show");
        });
    }

Best Answer

Nowadays (2016) in Chrome Dev Tools console, you can quickly execute this function below to show all event listeners that have been attached to an element.

getEventListeners(document.querySelector('your-element-selector'));
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