Question

Is there a way to retrieve the element source of an inline javaScript call?

I have a button like this:

<button onclick="doSomething('param')" id="id_button">action</button>

Note:

• the button is generated from server
• I cannot modify the generation process
• several buttons are generated on the page, I have control only on client side.

What I have tried:

function doSomething(param){
    var source = event.target || event.srcElement;
    console.log(source);
}

On firebug I get event is not defined

Edit:
After some answers, an override of the event handling using jQuery is very acceptable. My issue is how to call the original onClick function with it’s original prameters, and without knowing the function name.

code:

<button onclick="doSomething('param')" id="id_button1">action1</button>
<button onclick="doAnotherSomething('param1', 'param2')" id="id_button1">action2</button>.
<button onclick="doDifferentThing()" id="id_button3">action3</button>
.
.
and so on..

So the override would be:

$(document).on('click', 'button', function(e) {
  e.preventDefault();
  var action = $(this).attr('onclick');
  /**
   * What to do here to call
   * - doSomething(this, 'param'); if button1 is clicked
   * - doAnotherSomething(this, 'param1', 'param2'); if button2 is clicked
   * - doDifferentThing(this); if button3 is clicked
   * there are many buttons with many functions..
   */
});

Answer 1

You should change the generated HTML to not use inline javascript, and use addEventListener instead.

If you can not in any way change the HTML, you could get the onclick attributes, the functions and arguments used, and “convert” it to unobtrusive javascript instead by removing the onclick handlers, and using event listeners.

We’d start by getting the values from the attributes

$('button').each(function(i, el) {
    var funcs = [];

	$(el).attr('onclick').split(';').map(function(item) {
    	var fn     = item.split('(').shift(),
        	params = item.match(/\(([^)]+)\)/), 
            args;
            
        if (params && params.length) {
        	args = params[1].split(',');
            if (args && args.length) {
                args = args.map(function(par) {
            		return par.trim().replace(/('")/g,"");
            	});
            }
        }
        funcs.push([fn, args||[]]);
    });
  
    $(el).data('args', funcs); // store in jQuery's $.data
  
    console.log( $(el).data('args') );
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button onclick="doSomething('param')" id="id_button1">action1</button>
<button onclick="doAnotherSomething('param1', 'param2')" id="id_button1">action2</button>.
<button onclick="doDifferentThing()" id="id_button3">action3</button>

That gives us an array of all and any global methods called by the onclick attribute, and the arguments passed, so we can replicate it.

Then we’d just remove all the inline javascript handlers

$('button').removeAttr('onclick')

and attach our own handlers

$('button').on('click', function() {...}

Inside those handlers we’d get the stored original function calls and their arguments, and call them.
As we know any function called by inline javascript are global, we can call them with window[functionName].apply(this-value, argumentsArray), so

$('button').on('click', function() {
    var element = this;
    $.each(($(this).data('args') || []), function(_,fn) {
        if (fn[0] in window) window[fn[0]].apply(element, fn[1]);
    });
});

And inside that click handler we can add anything we want before or after the original functions are called.

A working example

$('button').each(function(i, el) {
    var funcs = [];

	$(el).attr('onclick').split(';').map(function(item) {
    	var fn     = item.split('(').shift(),
        	params = item.match(/\(([^)]+)\)/), 
            args;
            
        if (params && params.length) {
        	args = params[1].split(',');
            if (args && args.length) {
                args = args.map(function(par) {
            		return par.trim().replace(/('")/g,"");
            	});
            }
        }
        funcs.push([fn, args||[]]);
    });
    $(el).data('args', funcs);
}).removeAttr('onclick').on('click', function() {
	console.log('click handler for : ' + this.id);
  
	var element = this;
	$.each(($(this).data('args') || []), function(_,fn) {
    	if (fn[0] in window) window[fn[0]].apply(element, fn[1]);
    });
  
    console.log('after function call --------');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<button onclick="doSomething('param');" id="id_button1">action1</button>
<button onclick="doAnotherSomething('param1', 'param2')" id="id_button2">action2</button>.
<button onclick="doDifferentThing()" id="id_button3">action3</button>

<script>
	function doSomething(arg) { console.log('doSomething', arg) }
    function doAnotherSomething(arg1, arg2) { console.log('doAnotherSomething', arg1, arg2) }
    function doDifferentThing() { console.log('doDifferentThing','no arguments') }
</script>