resize

文档视图调整大小时会触发 resize 事件。

基本信息

规范

DOM L3, CSSOM View

接口

UIEvent

是否冒泡

是否可取消默认

事件目标

defaultView (window)

默认行为

None

属性

Property Type Description
target 只读 EventTarget The event target (the topmost target in the DOM tree).
type 只读 DOMString The type of event.
bubbles 只读 Boolean (en-US) Whether the event normally bubbles or not.
cancelable 只读 Boolean (en-US) Whether the event is cancellable or not.
view 只读 WindowProxy document.defaultView (window of the document)
detail 只读 long (float) 0.

案例

由于 resize 事件可以以较高的速率触发,因此事件处理程序不应该执行计算开销很大的操作 (如 DOM 修改)。相反,建议使用requestAnimationFrame, setTimeout (en-US) or customEvent, 比如:

requestAnimationFrame + customEvent

;(function() {
    var throttle = function(type, name, obj) {
        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
    ...
  }

}());