In response to: http://stackoverflow.com/questions/29916874/can-you-tell-if-one-element-is-touching-another-using-javascript
Created
April 30, 2015 14:34
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Detect Collision
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<div class="box" id="box1">1</div> | |
<div class="box" id="box2">2</div> | |
<div class="box" id="box3">3</div> | |
<div class="box" id="box4">4</div> |
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var boxes = document.querySelectorAll('.box'); | |
for (var i = 0; i < boxes.length; i++) { | |
if (boxes[i].addEventListener) { | |
boxes[i].addEventListener('click', clickHandler); | |
} else { | |
boxes[i].attachEvent('onclick', clickHandler); | |
} | |
} | |
var detectOverlap = (function () { | |
function getPositions(elem) { | |
var pos = elem.getBoundingClientRect(); | |
return [[pos.left, pos.right], [pos.top, pos.bottom]]; | |
} | |
function comparePositions(p1, p2) { | |
var r1, r2; | |
r1 = p1[0] < p2[0] ? p1 : p2; | |
r2 = p1[0] < p2[0] ? p2 : p1; | |
return r1[1] > r2[0] || r1[0] === r2[0]; | |
} | |
return function (a, b) { | |
var pos1 = getPositions(a), | |
pos2 = getPositions(b); | |
return comparePositions(pos1[0], pos2[0]) && comparePositions(pos1[1], pos2[1]); | |
}; | |
})(); | |
function clickHandler(e) { | |
var elem = e.target, | |
elems = document.querySelectorAll('.box'), | |
elemList = Array.prototype.slice.call(elems), | |
within = elemList.indexOf(elem), | |
touching = []; | |
if (within !== -1) { | |
elemList.splice(within, 1); | |
} | |
for (var i = 0; i < elemList.length; i++) { | |
if (detectOverlap(elem, elemList[i])) { | |
touching.push(elemList[i].id); | |
} | |
} | |
if (touching.length) { | |
alert(elem.id + ' touches ' + touching.join(' and ') + '.'); | |
} else { | |
alert(elem.id + ' touches nothing.') | |
} | |
} |
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#box1 { | |
background-color: LightSeaGreen; | |
} | |
#box2 { | |
top: 25px; | |
left: -25px; | |
background-color: SandyBrown; | |
} | |
#box3 { | |
left: -50px; | |
background-color: SkyBlue; | |
} | |
#box4 { | |
background-color: SlateGray; | |
} | |
.box { | |
position: relative; | |
display: inline-block; | |
width: 100px; | |
height: 100px; | |
color: White; | |
font: bold 72px sans-serif; | |
line-height: 100px; | |
text-align: center; | |
cursor: pointer; | |
} | |
.box:hover { | |
color: Black; | |
} |
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