js计算图片宽高并且定位图片位置并且图片的宽高和定位不能超过父元

// 计算图片宽高并且定位图片位置并且图片的宽高和定位不能超过父元素的大小

functionposition(el,img) {

varimgwidth=img.width

varimgheight=img.height

varparent=el.parentNode

varparentwidth=parent.clientWidth||parent.offsetWidth

varparentheight=parent.clientHeight||parent.offsetHeight

if(imgwidth<=parentwidth) {

if(imgheight>=parentheight) {

imgwidth=imgwidth/ (imgheight/parentheight)

imgheight=parentheight

}

}else{

if(imgheight/ (imgwidth/parentwidth) <=parentheight) {

imgheight=imgheight/ (imgwidth/parentwidth)

imgwidth=parentwidth

}else{

imgwidth=imgwidth/ (imgheight/parentheight)

imgheight=parentheight

}

}

conststyle=el.style

style.position='absolute'

style.width=imgwidth+'px'

style.height=imgheight+'px'

style.left= (parentwidth-imgwidth) /2+'px'

style.top= (parentheight-imgheight) /2+'px'

style.visibility='visible'

}

exportdefaultfunctionpositionImg(el) {

el.removeAttribute('style')

if(el.getAttribute('noPosition') ==='') {

el.style.visibility='visible'

return

}

el.removeAttribute('style')

constimg=newImage()

img.onload=function() {

position(el,img)

}

img.src=el.src

}