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const vueSticky = {}
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let listenAction
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vueSticky.install = Vue => {
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Vue.directive('sticky', {
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inserted(el, binding) {
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const params = binding.value || {}
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const stickyTop = params.stickyTop || 0
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const zIndex = params.zIndex || 1000
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const elStyle = el.style
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elStyle.position = '-webkit-sticky'
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elStyle.position = 'sticky'
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// if the browser support css sticky（Currently Safari, Firefox and Chrome Canary）
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// if (~elStyle.position.indexOf('sticky')) {
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// elStyle.top = `${stickyTop}px`;
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// elStyle.zIndex = zIndex;
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// return
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// }
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const elHeight = el.getBoundingClientRect().height
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const elWidth = el.getBoundingClientRect().width
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elStyle.cssText = `top: ${stickyTop}px; z-index: ${zIndex}`
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const parentElm = el.parentNode || document.documentElement
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const placeholder = document.createElement('div')
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placeholder.style.display = 'none'
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placeholder.style.width = `${elWidth}px`
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placeholder.style.height = `${elHeight}px`
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parentElm.insertBefore(placeholder, el)
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let active = false
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const getScroll = (target, top) => {
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const prop = top ? 'pageYOffset' : 'pageXOffset'
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const method = top ? 'scrollTop' : 'scrollLeft'
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let ret = target[prop]
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if (typeof ret !== 'number') {
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ret = window.document.documentElement[method]
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}
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return ret
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}
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const sticky = () => {
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if (active) {
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return
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}
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if (!elStyle.height) {
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elStyle.height = `${el.offsetHeight}px`
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}
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elStyle.position = 'fixed'
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elStyle.width = `${elWidth}px`
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placeholder.style.display = 'inline-block'
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active = true
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}
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const reset = () => {
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if (!active) {
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return
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}
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elStyle.position = ''
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placeholder.style.display = 'none'
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active = false
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}
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const check = () => {
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const scrollTop = getScroll(window, true)
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const offsetTop = el.getBoundingClientRect().top
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if (offsetTop < stickyTop) {
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sticky()
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} else {
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if (scrollTop < elHeight + stickyTop) {
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reset()
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}
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}
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}
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listenAction = () => {
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check()
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}
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window.addEventListener('scroll', listenAction)
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},
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unbind() {
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window.removeEventListener('scroll', listenAction)
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}
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})
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}
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export default vueSticky
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