event.which === 1 ensures it's a left-click (when using jQuery).
But you should also think about modifier keys: ctrlcmdshiftalt
If you're only interested in catching simple, unmodified left-clicks, you can do something like this:
var isSimpleClick = function (event) {
return !(
event.which !== 1 || // not a left click
event.metaKey || // "open link in new tab" (mac)
event.ctrlKey || // "open link in new tab" (windows/linux)
event.shiftKey || // "open link in new window"
event.altKey // "save link as"
);
};
$('a').on('click', function (event) {
if (isSimpleClick(event)) {
event.preventDefault();
// do something...
}
});