What s the difference between event stopPropagation and event preventDefault

Question

They seem to be doing the same thing    Is one modern and one old  Or are they supported by different browsers   When I handle events myself  without framework  I just always check for both and execute both if present   I also return false  but I have the feeling that doesn t work with events attached with node addEventListener       So why both  Should I keep checking for both  Or is there actually a difference     I know  a lot of questions  but they re all sort of the same

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event preventDefault    Stops the default action of an element from happening   event stopPropagation    Prevents the event from bubbling up the DOM tree  preventing any parent handlers from being notified of the event   For example  if there is a link with a click method attached inside of a DIV or FORM that also has a click method attached  it will prevent the DIV or FORM click method from firing

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stopPropagation prevents further propagation of the current event in the capturing and bubbling phases  preventDefault prevents the default action the browser makes on that event  Examples preventDefault  x000D   x000D      but   click function  event      event preventDefault          foo   click function        alert  parent click event fired       x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt   lt div id  foo  gt     lt button id  but  gt button lt  button gt   lt  div gt  x000D   x000D   x000D   stopPropagation  x000D   x000D      but   click function  event      event stopPropagation          foo   click function        alert  parent click event fired       x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt   lt div id  foo  gt     lt button id  but  gt button lt  button gt   lt  div gt  x000D   x000D   x000D   With stopPropagation  only the button s click handler is called while the div s click handler never fires  Where as if you use preventDefault  only the browser s default action is stopped but the div s click handler still fires  Below are some docs on the DOM event properties and methods from MDN   event cancelBubble event preventDefault   event returnValue event stopPropagation    For IE9 and FF you can just use preventDefault  amp  stopPropagation  To support IE8 and lower replace stopPropagation with cancelBubble and replace preventDefault with returnValue

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TL DRevent preventDefault   Prevents the browsers default behaviour  such as opening a link   but does not stop the event from bubbling up the DOM  event stopPropagation  Prevents the event from bubbling up the DOM  but does not stop the browsers default behaviour  return false Usually seen in jQuery code  it Prevents the browsers default behaviour  Prevents the event from bubbling up the DOM  and immediately Returns from any callback   One should checkout this really nice  amp  easy 4 min read with examples from where the above piece was copied from

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Terminology  From quirksmode org     Event capturing  When you use event capturing                      ---------------   -----------------   element1                              -----------   -----------            element2                           -------------------------                Event CAPTURING            -----------------------------------   the event handler of element1 fires first  the event handler of element2 fires last   Event bubbling  When you use event bubbling                      ---------------   -----------------   element1                              -----------   -----------            element2                           -------------------------                Event BUBBLING             -----------------------------------   the event handler of element2 fires first  the event handler of element1 fires last   Any event taking place in the W3C event model is first captured until it reaches the target element and then bubbles up again                              -----------------   --   -----------------   element1                                     -------------   --   -----------            element2                                  --------------------------------                W3C event model                   ------------------------------------------     Interface  From w3 org  for event capture      If the capturing EventListener wishes to prevent further processing of   the event from occurring it may call the stopPropagation method of the   Event interface  This will prevent further dispatch of the event    although additional EventListeners registered at the same hierarchy   level will still receive the event  Once an event s stopPropagation   method has been called  further calls to that method have no   additional effect  If no additional capturers exist and   stopPropagation has not been called  the event triggers the   appropriate EventListeners on the target itself    For event bubbling      Any event handler may choose to prevent further event propagation by   calling the stopPropagation method of the Event interface  If any   EventListener calls this method  all additional EventListeners on the   current EventTarget will be triggered but bubbling will cease at that   level  Only one call to stopPropagation is required to prevent further   bubbling    For event cancelation      Cancelation is accomplished by calling the Event s preventDefault   method  If one or more EventListeners call preventDefault during   any phase of event flow the default action will be canceled    Examples  In the following examples  a click on the hyperlink in the web browser triggers the event s flow  the event listeners are executed  and the event target s default action  a new tab is opened    HTML    lt div id  a  gt     lt a id  b  href  http   www google com   target   blank  gt Google lt  a gt   lt  div gt   lt p id  c  gt  lt  p gt    JavaScript   var el   document getElementById  c     function capturingOnClick1 ev        el innerHTML     DIV event capture lt br gt       function capturingOnClick2 ev        el innerHTML     A event capture lt br gt       function bubblingOnClick1 ev        el innerHTML     DIV event bubbling lt br gt       function bubblingOnClick2 ev        el innerHTML     A event bubbling lt br gt          The 3rd parameter useCapture makes the event listener capturing  false by default  document getElementById  a   addEventListener  click   capturingOnClick1  true   document getElementById  b   addEventListener  click   capturingOnClick2  true   document getElementById  a   addEventListener  click   bubblingOnClick1  false   document getElementById  b   addEventListener  click   bubblingOnClick2  false     Example 1  it results in the output  DIV event capture A event capture A event bubbling DIV event bubbling   Example 2  adding stopPropagation   to the function  function capturingOnClick1 ev        el innerHTML     DIV event capture lt br gt        ev stopPropagation        results in the output  DIV event capture   The event listener prevented further downward and upward propagation of the event  However it did not prevent the default action  a new tab opening    Example 3  adding stopPropagation   to the function  function capturingOnClick2 ev        el innerHTML     A event capture lt br gt        ev stopPropagation        or the function  function bubblingOnClick2 ev        el innerHTML     A event bubbling lt br gt        ev stopPropagation        results in the output  DIV event capture A event capture A event bubbling   This is because both event listeners are registered on the same event target  The event listeners prevented further upward propagation of the event  However they did not prevent the default action  a new tab opening    Example 4  adding preventDefault   to any function  for instance  function capturingOnClick1 ev        el innerHTML     DIV event capture lt br gt        ev preventDefault        prevents a new tab from opening

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return false     return false  does 3 separate things when you call it    event preventDefault       It stops the browsers default behaviour  event stopPropagation       It prevents the event from propagating  or    bubbling up     the DOM  Stops callback execution and returns immediately when called    Note that this behaviour differs from normal  non-jQuery  event handlers  in which  notably  return false does not stop the event from bubbling up   preventDefault       preventDefault    does one thing  It stops the browsers default behaviour   When to use them     We know what they do but when to use them  Simply it depends on what you want to accomplish  Use preventDefault    if you want to    just    prevent the default browser behaviour  Use return false  when you want to prevent the default browser behaviour and prevent the event from propagating the DOM  In most situations where you would use return false  what you really want is preventDefault     Examples     Let   s try to understand with examples   We will see pure JAVASCRIPT example  Example 1    x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  executeChild    gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    function executeChild     x000D      alert  Link Clicked    x000D      x000D   x000D    function executeParent     x000D      alert  div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D       Run the above code you will see the hyperlink    Click here to visit   stackoverflow com    now if you click on that link first you will get   the javascript alert Link Clicked Next you will get the javascript   alert div Clicked and immediately you will be redirected to   stackoverflow com    Example 2    x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  executeChild    gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    function executeChild     x000D      event preventDefault    x000D      event currentTarget innerHTML    Click event prevented  x000D      alert  Link Clicked    x000D      x000D   x000D    function executeParent     x000D      alert  div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D       Run the above code you will see the hyperlink    Click here to visit   stackoverflow com    now if you click on that link first you will get   the javascript alert Link Clicked Next you will get the javascript   alert div Clicked Next you will see the hyperlink    Click here to   visit stackoverflow com    replaced by the text    Click event prevented      and you will not be redirected to stackoverflow com  This is due   to event preventDefault   method we used to prevent the default click   action to be triggered    Example 3    x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  executeChild    gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    function executeChild     x000D      event stopPropagation    x000D      event currentTarget innerHTML    Click event prevented  x000D      alert  Link Clicked    x000D      x000D   x000D    function executeParent     x000D      alert  div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D       This time if you click on Link the function executeParent   will not   be called and you will not get the javascript alert div Clicked   this time  This is due to us having prevented the propagation to the   parent div using event stopPropagation   method  Next you will see the   hyperlink    Click here to visit stackoverflow com    replaced by the text      Click event is going to be executed    and immediately you will be   redirected to stackoverflow com  This is because we haven   t prevented   the default click action from triggering this time using   event preventDefault   method    Example 4    x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  executeChild    gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    function executeChild     x000D      event preventDefault    x000D      event stopPropagation    x000D      event currentTarget innerHTML    Click event prevented  x000D      alert  Link Clicked    x000D      x000D   x000D    function executeParent     x000D      alert  Div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D       If you click on the Link  the function executeParent   will not be   called and you will not get the javascript alert  This is due to us   having prevented the propagation to the parent div using   event stopPropagation   method  Next you will see the hyperlink    Click   here to visit stackoverflow com    replaced by the text    Click event   prevented    and you will not be redirected to stackoverflow com  This   is because we have prevented the default click action from triggering   this time using event preventDefault   method    Example 5      For return false I have three examples and all appear to be doing the exact same thing  just returning false   but in reality the   results are quite different  Here s what actually happens in each of   the above    cases    Returning false from an inline event handler prevents the browser from navigating to the link address  but it doesn t stop the event from propagating through the DOM  Returning false from a jQuery event handler prevents the browser from navigating to the link address and it stops the event from propagating through the DOM  Returning false from a regular DOM event handler does absolutely nothing    Will see all three example    Inline return false     x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  return false  gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    var link   document querySelector  a    x000D   x000D    link addEventListener  click   function     x000D      event currentTarget innerHTML    Click event prevented using inline html  x000D      alert  Link Clicked    x000D        x000D   x000D   x000D    function executeParent     x000D      alert  Div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D     Returning false from a jQuery event handler     x000D   x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt  x000D   lt div gt  x000D     lt a href  https   stackoverflow com  gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D       a   click function event    x000D      alert  Link Clicked    x000D         a   text  Click event prevented using return FALSE    x000D         a   contents   unwrap    x000D      return false  x000D        x000D       div   click function event    x000D      alert  Div clicked    x000D        x000D   lt  script gt  x000D   x000D   x000D     Returning false from a regular DOM event handler     x000D   x000D   lt div onclick  executeParent    gt  x000D     lt a href  https   stackoverflow com  onclick  executeChild    gt Click here to visit stackoverflow com lt  a gt  x000D   lt  div gt  x000D   lt script gt  x000D    function executeChild     x000D      event currentTarget innerHTML    Click event prevented  x000D      alert  Link Clicked    x000D      return false x000D      x000D   x000D    function executeParent     x000D      alert  Div Clicked    x000D      x000D   lt  script gt  x000D   x000D   x000D    Hope these examples are clear  Try executing all these examples in a html file to see how they work

User · Answer

x000D   x000D      but   click function event   x000D  console log  hello    x000D    event preventDefault    x000D       x000D   x000D   x000D      foo   click function    x000D   alert  parent click event fired      x000D      x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt  x000D   lt div id  foo  gt  x000D     lt button id  but  gt button lt  button gt  x000D   lt  div gt  x000D   x000D   x000D

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Event preventDefault- stops browser default behaviour  Now comes what is browser default behaviour  Assume you have a anchor tag and it has got a href attribute and this anchor tag is nested inside a div tag which has got a click event  Default behaviour of anchor tag is when clicked on the anchor tag it should navigate  but what event preventDefault does is it stops the navigation in this case  But it never stops the bubbling of event or escalation of event i e   lt div class  container  gt    lt a href     class  element  gt Click Me  lt  a gt   lt  div gt       container   on  click   function e     console log  container was clicked             element   on  click   function e      e preventDefault       Now link won t go anywhere   console log  element was clicked          The result will be    element was clicked    container was clicked   Now event StopPropation it stops bubbling of event or escalation of event  Now with above example       container   on  click   function e      console log  container was clicked             element   on  click   function e      e preventDefault       Now link won t go anywhere   e stopPropagation       Now the event won t bubble up  console log  element was clicked          Result will be    element was clicked   For more info refer this link  https   codeplanet io preventdefault-vs-stoppropagation-vs-stopimmediatepropagation

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This is the quote from here  Event preventDefault  The preventDefault method prevents an event from carrying out its default functionality   For example  you would use preventDefault on an A element to stop clicking that element from leaving the current page     clicking the link will  not  allow the user to leave the page  myChildElement onclick   function e         e preventDefault         console log  brick me            clicking the parent node will run the following console statement because event propagation occurs logo parentNode onclick   function e         console log  you bricked my child           While the element s default functionality is bricked  the event continues to bubble up the DOM   Event stopPropagation  The second method  stopPropagation  allows the event s default functionality to happen but prevents the event from propagating     clicking the element will allow the default action to occur but propagation will be stopped    myChildElement onclick   function e         e stopPropagation        console log  prop stop  no bubbles            since propagation was stopped by the child element s onClick  this message will never be seen  myChildElement parentNode onclick   function e         console log  you will never see this message           stopPropagation effectively stops parent elements from knowing about a given event on its child        While a simple stop  method allows us to quickly handle events  it s   important to think about what exactly you want to happen with   bubbling   I d bet that all a developer really wants is preventDefault   90  of the time   Incorrectly  stopping  an event could cause you   numerous troubles down the line  your plugins may not work and your   third party plugins could be bricked   Or worse yet -- your code   breaks other functionality on a site

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