Question

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I trying to get the target element’s id when function fired, but this keyword returns undefined

— HTML file —

<a href="#link_1" id="id_0" onclick = "getElement('parms1', 'parms2', 'parms3')">0</a>
<a href="#link_2" id="id_1" onclick = "getElement('parms1', 'parms2', 'parms3')">1</a>
<a href="#link_1" id="id_2" onclick = "getElement('parms1', 'parms2', 'parms3')">2</a>

— Js file —

function getElement = function(a, b, c){
    // trying to get the clicked element
    alert(this); // returns 'undefined'
}

Note: I can’t modify / add / remove parameters in onclick function, but I can add / remove parameters in js file

Problem: How to identify that which element was clicked without modifying the onclick function parameters?

Answer 1

Simple fix:

Change the HTML to:

<a href="#link_1" id="id_0" onclick = "getElement('parms1', 'parms2', 'parms3',this,event)">0</a>

And the function definition to:

//function getElement = function(){};doesn't really make sense...
function getElement (a, b, c,clicked,e)
{
    alert(clicked.id);//alerts id of clicked link
    alert((e.target || e.srcElement).id);//via the event object
}

So the choice is yours, either pass this and event to the function, or just event, or just this and you’re good to go.

You might want to look into delegating this type of events, though