The resize event is fired when the document view has been resized.

General info

Specifications
DOM L3, CSSOM View
Interface
UIEvent
Bubbles
No
Cancelable
No
Target
defaultView (window)
Default Action
None

Properties

Property Type Description
target Read only EventTarget The event target (the topmost target in the DOM tree).
type Read only DOMString The type of event.
bubbles Read only boolean Does the event normally bubble?
cancelable Read only boolean Is it possible to cancel the event?
view Read only WindowProxy document.defaultView (window of the document)
detail Read only long (float) 0.

Example

Since resize events can fire at a high rate, the event handler shouldn't execute computationally expensive operations such as DOM modifications. Instead, it is recommended to throttle the event using requestAnimationFrame, setTimeout or customEvent, as follows:

requestAnimationFrame + customEvent

;(function() {
    var throttle = function(type, name, obj) {
        var obj = obj || window;
        var running = false;
        var func = function() {
            if (running) { return; }
            running = true;
            requestAnimationFrame(function() {
                obj.dispatchEvent(new CustomEvent(name));
                running = false;
            });
        };
        obj.addEventListener(type, func);
    };

    /* init - you can init any event */
    throttle("resize", "optimizedResize");
})();

// handle event
window.addEventListener("optimizedResize", function() {
    console.log("Resource conscious resize callback!");
});

 

requestAnimationFrame

var optimizedResize = (function() {

    var callbacks = [],
        running = false;

    // fired on resize event
    function resize() {

        if (!running) {
            running = true;

            if (window.requestAnimationFrame) {
                window.requestAnimationFrame(runCallbacks);
            } else {
                setTimeout(runCallbacks, 66);
            }
        }

    }

    // run the actual callbacks
    function runCallbacks() {

        callbacks.forEach(function(callback) {
            callback();
        });

        running = false;
    }

    // adds callback to loop
    function addCallback(callback) {

        if (callback) {
            callbacks.push(callback);
        }

    }

    return {
        // public method to add additional callback
        add: function(callback) {
            if (!callbacks.length) {
                window.addEventListener('resize', resize);
            }
            addCallback(callback);
        }
    }
}());

// start process
optimizedResize.add(function() {
    console.log('Resource conscious resize callback!')
});
 

setTimeout

(function() {

  window.addEventListener("resize", resizeThrottler, false);

  var resizeTimeout;
  function resizeThrottler() {
    // ignore resize events as long as an actualResizeHandler execution is in the queue
    if ( !resizeTimeout ) {
      resizeTimeout = setTimeout(function() {
        resizeTimeout = null;
        actualResizeHandler();
     
       // The actualResizeHandler will execute at a rate of 15fps
       }, 66);
    }
  }

  function actualResizeHandler() {
    // handle the resize event
    ...
  }

}());

Document Tags and Contributors

Last updated by: cvrebert,