是否有可能获得鼠标位置与JavaScript页面加载后,没有任何鼠标移动事件(不移动鼠标)?
当前回答
重复@超新星的回答,这里有一个使用ES6类的方法,它在你的回调中保持正确的上下文:
class Mouse { constructor() { this.x = 0; this.y = 0; this.callbacks = { mouseenter: [], mousemove: [], }; } get xPos() { return this.x; } get yPos() { return this.y; } get position() { return `${this.x},${this.y}`; } addListener(type, callback) { document.addEventListener(type, this); // Pass `this` as the second arg to keep the context correct this.callbacks[type].push(callback); } // `handleEvent` is part of the browser's `EventListener` API. // https://developer.mozilla.org/en-US/docs/Web/API/EventListener/handleEvent handleEvent(event) { const isMousemove = event.type === 'mousemove'; const isMouseenter = event.type === 'mouseenter'; if (isMousemove || isMouseenter) { this.x = event.pageX; this.y = event.pageY; } this.callbacks[event.type].forEach((callback) => { callback(); }); } } const mouse = new Mouse(); mouse.addListener('mouseenter', () => console.log('mouseenter', mouse.position)); mouse.addListener('mousemove', () => console.log('mousemove A', mouse.position)); mouse.addListener('mousemove', () => console.log('mousemove B', mouse.position));
其他回答
真实的答案:不,这是不可能的。
OK, I have just thought of a way. Overlay your page with a div that covers the whole document. Inside that, create (say) 2,000 x 2,000 <a> elements (so that the :hover pseudo-class will work in IE 6, see), each 1 pixel in size. Create a CSS :hover rule for those <a> elements that changes a property (let's say font-family). In your load handler, cycle through each of the 4 million <a> elements, checking currentStyle / getComputedStyle() until you find the one with the hover font. Extrapolate back from this element to get the co-ordinates within the document.
N.b.,别这样。
重复@超新星的回答,这里有一个使用ES6类的方法,它在你的回调中保持正确的上下文:
class Mouse { constructor() { this.x = 0; this.y = 0; this.callbacks = { mouseenter: [], mousemove: [], }; } get xPos() { return this.x; } get yPos() { return this.y; } get position() { return `${this.x},${this.y}`; } addListener(type, callback) { document.addEventListener(type, this); // Pass `this` as the second arg to keep the context correct this.callbacks[type].push(callback); } // `handleEvent` is part of the browser's `EventListener` API. // https://developer.mozilla.org/en-US/docs/Web/API/EventListener/handleEvent handleEvent(event) { const isMousemove = event.type === 'mousemove'; const isMouseenter = event.type === 'mouseenter'; if (isMousemove || isMouseenter) { this.x = event.pageX; this.y = event.pageY; } this.callbacks[event.type].forEach((callback) => { callback(); }); } } const mouse = new Mouse(); mouse.addListener('mouseenter', () => console.log('mouseenter', mouse.position)); mouse.addListener('mousemove', () => console.log('mousemove A', mouse.position)); mouse.addListener('mousemove', () => console.log('mousemove B', mouse.position));
如果你渲染2000 x 2000 <a>个元素,@Tim Down的答案是不性能的:
OK, I have just thought of a way. Overlay your page with a div that covers the whole document. Inside that, create (say) 2,000 x 2,000 elements (so that the :hover pseudo-class will work in IE 6, see), each 1 pixel in size. Create a CSS :hover rule for those elements that changes a property (let's say font-family). In your load handler, cycle through each of the 4 million elements, checking currentStyle / getComputedStyle() until you find the one with the hover font. Extrapolate back from this element to get the co-ordinates within the document. N.B. DON'T DO THIS.
但是你不需要一次呈现400万个元素,而是使用二分搜索。只需使用4 <a>元素即可:
第一步:考虑整个屏幕作为开始搜索区域 步骤2:将搜索区域分割成2 × 2 = 4个矩形<a>个元素 步骤3:使用getComputedStyle()函数确定鼠标悬停在哪个矩形中 步骤4:将搜索区域缩小到该矩形,并重复步骤2。
这样你将需要重复这些步骤最多11次,考虑到你的屏幕不超过2048px。
所以你将生成最多11 x 4 = 44 <a>个元素。
如果你不需要确定鼠标位置精确到一个像素,但说10px的精度是可以的。您将重复这些步骤最多8次,因此您将需要绘制最多8 x 4 = 32 <a>个元素。
生成并销毁<a>元素也不能执行,因为DOM通常很慢。相反,您可以重用初始的4 <a>元素,并在循环执行步骤时调整它们的顶部、左侧、宽度和高度。
现在,创建4 <a>也是多余的。相反,您可以在每个矩形中测试getComputedStyle()时重用相同的<a>元素。因此,不需要将搜索区域分割为2 × 2 <a>元素,只需要重复使用一个<a>元素,使用顶部和左侧样式属性移动它。
所以,所有你需要的是一个<a>元素改变它的宽度和高度最多11次,改变它的顶部和左侧最多44次,你就会有准确的鼠标位置。
这是我的解决方案。它导出窗口。currentMouseX和window。你可以在任何地方使用currentMouseY属性。它首先使用悬停元素的位置(如果有的话),然后监听鼠标移动来设置正确的值。
(function () {
window.currentMouseX = 0;
window.currentMouseY = 0;
// Guess the initial mouse position approximately if possible:
var hoveredElement = document.querySelectorAll(':hover');
hoveredElement = hoveredElement[hoveredElement.length - 1]; // Get the most specific hovered element
if (hoveredElement != null) {
var rect = hoveredElement.getBoundingClientRect();
// Set the values from hovered element's position
window.currentMouseX = window.scrollX + rect.x;
window.currentMouseY = window.scrollY + rect.y;
}
// Listen for mouse movements to set the correct values
window.addEventListener('mousemove', function (e) {
window.currentMouseX = e.pageX;
window.currentMouseY = e.pageY;
}, /*useCapture=*/true);
}())
来源:https://github.com/ocproducts/composr/commit/a851c19f925be20bc16bfe016be42924989f262e#diff-b162dc9c35a97618a96748639ff41251R1202
我实现了一个水平/垂直搜索,(首先让一个div充满垂直排列的竖线链接,然后让一个div充满水平排列的竖线链接,然后简单地看看哪个有悬停状态),就像Tim Down上面的想法,它工作得相当快。遗憾的是,不工作在Chrome 32上的KDE。
jsfiddle.net/5XzeE/4/
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