fastclick源码学习（1）

FastClick.prototype.onTouchStart = function(event) {
        var targetElement, touch, selection;
        // Ignore multiple touches, otherwise pinch-to-zoom is prevented if both fingers are on the FastClick element (issue #111).
        if (event.targetTouches.length > 1) {
            return true;
        }
        targetElement = this.getTargetElementFromEventTarget(event.target);
        touch = event.targetTouches[0];

        if (deviceIsIOS) {
      //这里先不研究
        }

        this.trackingClick = true;
        this.trackingClickStart = event.timeStamp;
        this.targetElement = targetElement;

        this.touchStartX = touch.pageX;
        this.touchStartY = touch.pageY;

        // Prevent phantom clicks on fast double-tap (issue #36)
        if ((event.timeStamp - this.lastClickTime) < this.tapDelay) {
            event.preventDefault();
        }
        return true;
    };

 1 FastClick.prototype.onTouchEnd = function(event) {
 2         var forElement, trackingClickStart, targetTagName, scrollParent, touch, targetElement = this.targetElement;
 3 
 4         if (!this.trackingClick) {
 5             return true;
 6         }
 7 
 8         // Prevent phantom clicks on fast double-tap (issue #36)
 9         if ((event.timeStamp - this.lastClickTime) < this.tapDelay) {
10             this.cancelNextClick = true;
11             return true;
12         }
13 
14         if ((event.timeStamp - this.trackingClickStart) > this.tapTimeout) {
15             return true;
16         }
17 
18         // Reset to prevent wrong click cancel on input (issue #156).
19         this.cancelNextClick = false;
20 
21         this.lastClickTime = event.timeStamp;
22 
23         trackingClickStart = this.trackingClickStart;
24         this.trackingClick = false;
25         this.trackingClickStart = 0;
26 
27         // On some iOS devices, the targetElement supplied with the event is invalid if the layer
28         // is performing a transition or scroll, and has to be re-detected manually. Note that
29         // for this to function correctly, it must be called *after* the event target is checked!
30         // See issue #57; also filed as rdar://13048589 .
31         if (deviceIsIOSWithBadTarget) {
32             touch = event.changedTouches[0];
33 
34             // In certain cases arguments of elementFromPoint can be negative, so prevent setting targetElement to null
35             targetElement = document.elementFromPoint(touch.pageX - window.pageXOffset, touch.pageY - window.pageYOffset) || targetElement;
36             targetElement.fastClickScrollParent = this.targetElement.fastClickScrollParent;
37         }
38 
39         targetTagName = targetElement.tagName.toLowerCase();
40         if (targetTagName === ‘label‘) {
41             forElement = this.findControl(targetElement);
42             if (forElement) {
43                 this.focus(targetElement);
44                 if (deviceIsAndroid) {
45                     return false;
46                 }
47 
48                 targetElement = forElement;
49             }
50         } else if (this.needsFocus(targetElement)) {
51 
52             // Case 1: If the touch started a while ago (best guess is 100ms based on tests for issue #36) then focus will be triggered anyway. Return early and unset the target element reference so that the subsequent click will be allowed through.
53             // Case 2: Without this exception for input elements tapped when the document is contained in an iframe, then any inputted text won‘t be visible even though the value attribute is updated as the user types (issue #37).
54             if ((event.timeStamp - trackingClickStart) > 100 || (deviceIsIOS && window.top !== window && targetTagName === ‘input‘)) {
55                 this.targetElement = null;
56                 return false;
57             }
58 
59             this.focus(targetElement);
60             this.sendClick(targetElement, event);
61 
62             // Select elements need the event to go through on iOS 4, otherwise the selector menu won‘t open.
63             // Also this breaks opening selects when VoiceOver is active on iOS6, iOS7 (and possibly others)
64             if (!deviceIsIOS || targetTagName !== ‘select‘) {
65                 this.targetElement = null;
66                 event.preventDefault();
67             }
68 
69             return false;
70         }
71 
72         if (!this.needsClick(targetElement)) {
73             event.preventDefault();
74             this.sendClick(targetElement, event);
75         }
76 
77         return false;
78     };

 1     FastClick.prototype.needsFocus = function(target) {
 2         switch (target.nodeName.toLowerCase()) {
 3         case ‘textarea‘:
 4             return true;
 5         case ‘select‘:
 6             return !deviceIsAndroid;
 7         case ‘input‘:
 8             switch (target.type) {
 9             case ‘button‘:
10             case ‘checkbox‘:
11             case ‘file‘:
12             case ‘image‘:
13             case ‘radio‘:
14             case ‘submit‘:
15                 return false;
16             }

 1 FastClick.prototype.needsClick = function(target) {
 2         switch (target.nodeName.toLowerCase()) {
 3 
 4         // Don‘t send a synthetic click to disabled inputs (issue #62)
 5         case ‘button‘:
 6         case ‘select‘:
 7         case ‘textarea‘:
 8             if (target.disabled) {
 9                 return true;
10             }
11 
12             break;
13         case ‘input‘:
14 
15             // File inputs need real clicks on iOS 6 due to a browser bug (issue #68)
16             if ((deviceIsIOS && target.type === ‘file‘) || target.disabled) {
17                 return true;
18             }
19 
20             break;
21         case ‘label‘:
22         case ‘iframe‘: // iOS8 homescreen apps can prevent events bubbling into frames
23         case ‘video‘:
24             return true;
25         }
26 
27         return (/\bneedsclick\b/).test(target.className);
28     };

 1     FastClick.prototype.sendClick = function(targetElement, event) {
 2         var clickEvent, touch;
 3 
 4         // On some Android devices activeElement needs to be blurred otherwise the synthetic click will have no effect (#24)
 5         if (document.activeElement && document.activeElement !== targetElement) {
 6             document.activeElement.blur();
 7         }
 8 
 9         touch = event.changedTouches[0];
10 
11         // Synthesise a click event, with an extra attribute so it can be tracked
12         clickEvent = document.createEvent(‘MouseEvents‘);
13         clickEvent.initMouseEvent(this.determineEventType(targetElement), true, true, window, 1, touch.screenX, touch.screenY, touch.clientX, touch.clientY, false, false, false, false, 0, null);
14         clickEvent.forwardedTouchEvent = true;
15         targetElement.dispatchEvent(clickEvent);
16     };