How to stop event propagation with inline onclick attribute?

Use event.stopPropagation().

<span onclick="event.stopPropagation(); alert('you clicked inside the header');">something inside the header</span>

For IE: window.event.cancelBubble = true

<span onclick="window.event.cancelBubble = true; alert('you clicked inside the header');">something inside the header</span>

There are two ways to get the event object from inside a function:

1. The first argument, in a W3C-compliant browser (Chrome, Firefox, Safari, IE9+)
2. The window.event object in Internet Explorer (<=8)

If you need to support legacy browsers that don't follow the W3C recommendations, generally inside a function you would use something like the following:

function(e) {
  var event = e || window.event;
  [...];
}

which would check first one, and then the other and store whichever was found inside the event variable. However in an inline event handler there isn't an e object to use. In that case you have to take advantage of the arguments collection which is always available and refers to the complete set of arguments passed to a function:

onclick="var event = arguments[0] || window.event; [...]"

However, generally speaking you should be avoiding inline event handlers if you need to to anything complicated like stopping propagation. Writing your event handlers separately and the attaching them to elements is a much better idea in the medium and long term, both for readability and maintainability.

Keep in mind that window.event is not supported in FireFox, and therefore it must be something along the lines of:

e.cancelBubble = true

Or, you can use the W3C standard for FireFox:

e.stopPropagation();

If you want to get fancy, you can do this:

function myEventHandler(e)
{
    if (!e)
      e = window.event;

    //IE9 & Other Browsers
    if (e.stopPropagation) {
      e.stopPropagation();
    }
    //IE8 and Lower
    else {
      e.cancelBubble = true;
    }
}

I cannot comment because of Karma so I write this as whole answer: According to the answer of Gareth (var e = arguments[0] || window.event; [...]) I used this oneliner inline on the onclick for a fast hack:

<div onclick="(arguments[0] || window.event).stopPropagation();">..</div>

I know it's late but I wanted to let you know that this works in one line. The braces return an event which has the stopPropagation-function attached in both cases, so I tried to encapsulate them in braces like in an if and....it works. :)

According to this page, in IE you need:

event.cancelBubble = true

Use separate handler, say:

function myOnClickHandler(th){
//say let t=$(th)
}

and in html do this:

<...onclick="myOnClickHandler(this); event.stopPropagation();"...>

Or even :

function myOnClickHandler(e){
  e.stopPropagation();
}

for:

<...onclick="myOnClickHandler(event)"...>

The best solution would be handle with the event through a javascript function, but in order to use a simple and quick solution using the html element directly, and once that the "event" and "window.event" are deprecated and not universally supported (https://developer.mozilla.org/en-US/docs/Web/API/Window/event), I suggest the following "hard code":

<div onclick="alert('blablabla'); (arguments[0] ? arguments[0].stopPropagation() : false);">...</div>

Event.preventDefault()

is the current norm, and the one thing that worked for me. See: https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault

    <button value=login onclick="login(event)">login</button>

//and in a script tag
function login(ev){
    ev.preventDefault()
    
    return false;
}

this worked in the latest Chrome, Opera, and IE. (the Mozilla page indicates Firefox would do it too, so I don't even test it!)