Check if an element has event listener on it. No jQuery [duplicate]

Question

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");         });     } 

Answer 1

Since 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')); 

Caution: This solution is only works for Chrome developer tools.