Tooltip插件可以让你把要显示的内容以弹出框的形式来展示，如：

因为自己在工作的过程中，用到了Tooltip这个插件，并且当时正想学习一下元素定位的问题，如：提示框显示的位置就是触发提示框元素的位置，可以配置在上、下、左、右等位置，所以就去看了源码。对于整个插件源码没有看全，但也学到了许多的知识点。能力有限，可能其中有认识错误的地方，以后再补充吧

1 使用方法不介绍 ，可以参照

Bootstrap 提示工具（Tooltip）插件

2 源码解析

+function ($) { 'use strict'; // TOOLTIP PUBLIC CLASS DEFINITION // =============================== var Tooltip = function (element, options) { this.type = this.options = this.enabled = this.timeout = this.hoverState = this.$element = null this.init('tooltip', element, options) } Tooltip.VERSION = '3.3.0' Tooltip.TRANSITION_DURATION = 150 //默认参数 Tooltip.DEFAULTS = { animation: true, placement: 'top', selector: false, template: '<div class="tooltip" role="tooltip"><div class="tooltip-arrow"></div><div class="tooltip-inner"></div></div>', trigger: 'hover focus', title: '', delay: 0, html: false, container: false, viewport: { selector: 'body', padding: 0 } } //初始化 Tooltip.prototype.init = function (type, element, options) { this.enabled = true this.type = type this.$element = $(element) //初始化参数 this.options = this.getOptions(options) this.$viewport = this.options.viewport && $(this.options.viewport.selector || this.options.viewport) //多个触发器 即触发函数 var triggers = this.options.trigger.split(' ') for (var i = triggers.length; i--;) { var trigger = triggers[i] if (trigger == 'click') { //绑定事件处理程序 //事件命名空间 'click.tooltip' //触发时执行$.proxy(this.toggle, this)返回的函数 this.$element.on('click.' + this.type, this.options.selector, $.proxy(this.toggle, this)) } else if (trigger != 'manual') { var eventIn = trigger == 'hover' ? 'mouseenter' : 'focusin' var eventOut = trigger == 'hover' ? 'mouseleave' : 'focusout' this.$element.on(eventIn + '.' + this.type, this.options.selector, $.proxy(this.enter, this)) this.$element.on(eventOut + '.' + this.type, this.options.selector, $.proxy(this.leave, this)) } } this.options.selector ? (this._options = $.extend({}, this.options, { trigger: 'manual', selector: '' })) : this.fixTitle() } Tooltip.prototype.getDefaults = function () { return Tooltip.DEFAULTS } //获得初始化参数 Tooltip.prototype.getOptions = function (options) { // this.$element.data() data-key = value 形式的属性获取 // 返回一个对象{key:value} // options > 元素属性 > 默认 options = $.extend({}, this.getDefaults(), this.$element.data(), options) //delay 为数字 特殊处理 //delay 为对象 delay:{ show: 500, hide: 100 } if (options.delay && typeof options.delay == 'number') { options.delay = { show: options.delay, hide: options.delay } } return options } Tooltip.prototype.getDelegateOptions = function () { var options = {} var defaults = this.getDefaults() this._options && $.each(this._options, function (key, value) { if (defaults[key] != value) options[key] = value }) return options } //提示框显示 Tooltip.prototype.enter = function (obj) { //obj是否是tooltip的实例 var self = obj instanceof this.constructor ? obj : $(obj.currentTarget).data('bs.' + this.type) //$tip.is(':visible') 该div是否可见 //可见时 只更新状态 然后直接返回 if (self && self.$tip && self.$tip.is(':visible')) { self.hoverState = 'in' return } //self 不存在 if (!self) { self = new this.constructor(obj.currentTarget, this.getDelegateOptions()) $(obj.currentTarget).data('bs.' + this.type, self) } //上次点击延时未显示 则取消显示 clearTimeout(self.timeout) //设置状态 self.hoverState = 'in' //delay: 数字 (默认 0) 或 对象 { show: 500, hide: 100 } //没有delay delay.show 时 直接显示 if (!self.options.delay || !self.options.delay.show) return self.show() //延时显示 self.options.delay.show:延时时间 self.timeout = setTimeout(function () { if (self.hoverState == 'in') self.show() }, self.options.delay.show) } //提示框隐藏 Tooltip.prototype.leave = function (obj) { var self = obj instanceof this.constructor ? obj : $(obj.currentTarget).data('bs.' + this.type) if (!self) { self = new this.constructor(obj.currentTarget, this.getDelegateOptions()) $(obj.currentTarget).data('bs.' + this.type, self) } clearTimeout(self.timeout) self.hoverState = 'out' if (!self.options.delay || !self.options.delay.hide) return self.hide() self.timeout = setTimeout(function () { if (self.hoverState == 'out') self.hide() }, self.options.delay.hide) } //提示框显示核心方法 Tooltip.prototype.show = function () { console.info(this) var e = $.Event('show.bs.' + this.type) if (this.hasContent() && this.enabled) { this.$element.trigger(e) //判断是否在根节点中 //this.$element[0] 转换为DOM对象 //.ownerDocument Document文档对象 //.documentElement 根节点 HTML标签 //$.contains 一个DOM节点是否包含另一个DOM节点。 var inDom = $.contains(this.$element[0].ownerDocument.documentElement, this.$element[0]) //调用preventDefault 或 不在根节点 return //事件对象中是否调用过 event.preventDefault() //event.preventDefault():阻止元素发生默认的行为 //如 当点击提交按钮时阻止对表单的提交 、 阻止以下 URL 的链接 if (e.isDefaultPrevented() || !inDom) return var that = this var $tip = this.tip() var tipId = this.getUID(this.type) //设置提示框的title this.setContent() $tip.attr('id', tipId) this.$element.attr('aria-describedby', tipId) //参数animation if (this.options.animation) $tip.addClass('fade') //参数placement 提示框的位置 top bottom left right var placement = typeof this.options.placement == 'function' ? this.options.placement.call(this, $tip[0], this.$element[0]) : this.options.placement // 判断placement是否包含"auto" var autoToken = /\s?auto?\s?/i var autoPlace = autoToken.test(placement) //包含 "auto"时 if (autoPlace) placement = placement.replace(autoToken, '') || 'top' $tip //detach() 删除匹配的对象 与remove()不同的是，所有绑定的事件、附加的数据等都会保留下来 .detach() .css({ top: 0, left: 0, display: 'block' }) .addClass(placement) .data('bs.' + this.type, this) //参数 container 向指定元素添加该提示框 //没有 添加到当前元素后面 this.options.container ? $tip.appendTo(this.options.container) : $tip.insertAfter(this.$element) //位置对象pos pos = {top: , right: , bottom: , left: , width: ,scroll:} var pos = this.getPosition() //提示框自身实际的 width height var actualWidth = $tip[0].offsetWidth var actualHeight = $tip[0].offsetHeight if (autoPlace) { var orgPlacement = placement var $container = this.options.container ? $(this.options.container) : this.$element.parent() var containerDim = this.getPosition($container) placement = placement == 'bottom' && pos.bottom + actualHeight > containerDim.bottom ? 'top' : placement == 'top' && pos.top - actualHeight < containerDim.top ? 'bottom' : placement == 'right' && pos.right + actualWidth > containerDim.width ? 'left' : placement == 'left' && pos.left - actualWidth < containerDim.left ? 'right' : placement $tip .removeClass(orgPlacement) .addClass(placement) } //计算提示框的偏移量 {top: , left: } var calculatedOffset = this.getCalculatedOffset(placement, pos, actualWidth, actualHeight) //应用并设置偏移量 this.applyPlacement(calculatedOffset, placement) var complete = function () { var prevHoverState = that.hoverState that.$element.trigger('shown.bs.' + that.type) that.hoverState = null if (prevHoverState == 'out') that.leave(that) } $.support.transition && this.$tip.hasClass('fade') ? $tip .one('bsTransitionEnd', complete) .emulateTransitionEnd(Tooltip.TRANSITION_DURATION) : complete() } } Tooltip.prototype.applyPlacement = function (offset, placement) { var $tip = this.tip() var width = $tip[0].offsetWidth var height = $tip[0].offsetHeight // manually read margins because getBoundingClientRect includes difference //获得提示框自身的外边距的值 var marginTop = parseInt($tip.css('margin-top'), 10) var marginLeft = parseInt($tip.css('margin-left'), 10) // we must check for NaN for ie 8/9 //是否是非数字 if (isNaN(marginTop)) marginTop = 0 if (isNaN(marginLeft)) marginLeft = 0 //计算的偏移量 + 自身的外边距 offset.top = offset.top + marginTop offset.left = offset.left + marginLeft // $.fn.offset doesn't round pixel values // so we use setOffset directly with our own function B-0 // 应用了offset.setOffset方法，传入了using参数，因为offset设置值的时候，不能四舍五入 $.offset.setOffset($tip[0], $.extend({ using: function (props) { $tip.css({ top: Math.round(props.top), left: Math.round(props.left) }) } }, offset), 0) //添加 in class 让提示框显示 $tip.addClass('in') // check to see if placing tip in new offset caused the tip to resize itself //获取显示后的提示框的宽和高 检查是否调整了自身的大小 var actualWidth = $tip[0].offsetWidth var actualHeight = $tip[0].offsetHeight if (placement == 'top' && actualHeight != height) { offset.top = offset.top + height - actualHeight } var delta = this.getViewportAdjustedDelta(placement, offset, actualWidth, actualHeight) if (delta.left) offset.left += delta.left else offset.top += delta.top var isVertical = /top|bottom/.test(placement) var arrowDelta = isVertical ? delta.left * 2 - width + actualWidth : delta.top * 2 - height + actualHeight var arrowOffsetPosition = isVertical ? 'offsetWidth' : 'offsetHeight' $tip.offset(offset) this.replaceArrow(arrowDelta, $tip[0][arrowOffsetPosition], isVertical) } Tooltip.prototype.replaceArrow = function (delta, dimension, isHorizontal) { this.arrow() .css(isHorizontal ? 'left' : 'top', 50 * (1 - delta / dimension) + '%') .css(isHorizontal ? 'top' : 'left', '') } //设置提示框的title Tooltip.prototype.setContent = function () { //div var $tip = this.tip() var title = this.getTitle() $tip.find('.tooltip-inner')[this.options.html ? 'html' : 'text'](title) $tip.removeClass('fade in top bottom left right') } Tooltip.prototype.hide = function (callback) { var that = this var $tip = this.tip() var e = $.Event('hide.bs.' + this.type) function complete() { if (that.hoverState != 'in') $tip.detach() that.$element .removeAttr('aria-describedby') .trigger('hidden.bs.' + that.type) callback && callback() } this.$element.trigger(e) if (e.isDefaultPrevented()) return $tip.removeClass('in') $.support.transition && this.$tip.hasClass('fade') ? $tip .one('bsTransitionEnd', complete) .emulateTransitionEnd(Tooltip.TRANSITION_DURATION) : complete() this.hoverState = null return this } Tooltip.prototype.fixTitle = function () { var $e = this.$element if ($e.attr('title') || typeof ($e.attr('data-original-title')) != 'string') { $e.attr('data-original-title', $e.attr('title') || '').attr('title', '') } } Tooltip.prototype.hasContent = function () { return this.getTitle() } //获取位置 Tooltip.prototype.getPosition = function ($element) { //不传入 则为当前点击元素 $element = $element || this.$element //转换为DOM对象 var el = $element[0] //是否是body元素 var isBody = el.tagName == 'BODY' //获取元素各边与页面上边和左边的距离 left right top bottom height width var elRect = el.getBoundingClientRect() //兼容IE8 没有 width height 则计算 if (elRect.width == null) { // width and height are missing in IE8, so compute them manually; see https://github.com/twbs/bootstrap/issues/14093 elRect = $.extend({}, elRect, { width: elRect.right - elRect.left, height: elRect.bottom - elRect.top }) } //当前元素相对于文档的偏移量 var elOffset = isBody ? { top: 0, left: 0 } : $element.offset() //垂直滚动条的距离 //document.documentElement.scrollTop 和 document.body.scrollTop 浏览器兼容 var scroll = { scroll: isBody ? document.documentElement.scrollTop || document.body.scrollTop : $element.scrollTop() } var outerDims = isBody ? { width: $(window).width(), height: $(window).height() } : null //合并 return $.extend({}, elRect, scroll, outerDims, elOffset) } //计算偏移量 Tooltip.prototype.getCalculatedOffset = function (placement, pos, actualWidth, actualHeight) { return placement == 'bottom' ? { top: pos.top + pos.height, left: pos.left + pos.width / 2 - actualWidth / 2 } : placement == 'top' ? { top: pos.top - actualHeight, left: pos.left + pos.width / 2 - actualWidth / 2 } : placement == 'left' ? { top: pos.top + pos.height / 2 - actualHeight / 2, left: pos.left - actualWidth } : { top: pos.top + pos.height / 2 - actualHeight / 2, left: pos.left + pos.width } } Tooltip.prototype.getViewportAdjustedDelta = function (placement, pos, actualWidth, actualHeight) { var delta = { top: 0, left: 0 } //默认参数 //viewport: { // selector: 'body', // padding: 0 //} //默认的话 this.$viewport = 'body' if (!this.$viewport) return delta var viewportPadding = this.options.viewport && this.options.viewport.padding || 0 //this.$viewport = 'body' width height为 window的 var viewportDimensions = this.getPosition(this.$viewport) console.info(viewportDimensions) if (/right|left/.test(placement)) { var topEdgeOffset = pos.top - viewportPadding - viewportDimensions.scroll var bottomEdgeOffset = pos.top + viewportPadding - viewportDimensions.scroll + actualHeight if (topEdgeOffset < viewportDimensions.top) { // top overflow delta.top = viewportDimensions.top - topEdgeOffset } else if (bottomEdgeOffset > viewportDimensions.top + viewportDimensions.height) { // bottom overflow delta.top = viewportDimensions.top + viewportDimensions.height - bottomEdgeOffset } } else { var leftEdgeOffset = pos.left - viewportPadding var rightEdgeOffset = pos.left + viewportPadding + actualWidth if (leftEdgeOffset < viewportDimensions.left) { // left overflow delta.left = viewportDimensions.left - leftEdgeOffset } else if (rightEdgeOffset > viewportDimensions.width) { // right overflow delta.left = viewportDimensions.left + viewportDimensions.width - rightEdgeOffset } } return delta } //提示框的title Tooltip.prototype.getTitle = function () { var title var $e = this.$element var o = this.options //先获取当前元素的data-original-title属性 //否则获取参数title title = $e.attr('data-original-title') || (typeof o.title == 'function' ? o.title.call($e[0]) : o.title) return title } //随机生成唯一id 0 -- 100000 id值 Tooltip.prototype.getUID = function (prefix) { //~~ 去掉小数部分 do prefix += ~~(Math.random() * 1000000) while (document.getElementById(prefix)) return prefix } //生成提示框的div //不存在 则用模板 //<div class="tooltip" role="tooltip"><div class="tooltip-arrow"></div><div class="tooltip-inner"></div></div> Tooltip.prototype.tip = function () { return (this.$tip = this.$tip || $(this.options.template)) } Tooltip.prototype.arrow = function () { return (this.$arrow = this.$arrow || this.tip().find('.tooltip-arrow')) } Tooltip.prototype.enable = function () { this.enabled = true } Tooltip.prototype.disable = function () { this.enabled = false } Tooltip.prototype.toggleEnabled = function () { this.enabled = !this.enabled } //click 事件触发时执行的函数 Tooltip.prototype.toggle = function (e) { //this tooltip实例对象 var self = this if (e) { //e.currentTarget 返回注册该事件处理程序的元素 self = $(e.currentTarget).data('bs.' + this.type) if (!self) { self = new this.constructor(e.currentTarget, this.getDelegateOptions()) $(e.currentTarget).data('bs.' + this.type, self) } } //判断提示框当前的状态 //true 当前显示 需要隐藏 //false 相反 self.tip().hasClass('in') ? self.leave(self) : self.enter(self) } Tooltip.prototype.destroy = function () { var that = this clearTimeout(this.timeout) this.hide(function () { that.$element.off('.' + that.type).removeData('bs.' + that.type) }) } // TOOLTIP PLUGIN DEFINITION // ========================= function Plugin(option) { return this.each(function () { var $this = $(this) //所选元素是否有 key为:bs.tooltip 对应的value值 var data = $this.data('bs.tooltip') //option为对象 options:option //option为字符串 则是方法 options:false var options = typeof option == 'object' && option //option是对象 执行初始化 ，并提供了选择器 var selector = options && options.selector //是destroy 方法 不执行 if (!data && option == 'destroy') return //tooltip初始化 if (selector) { //存在选择器，则将当前点击元素 bs.tooltip = {} 即去掉Tooltip实例 if (!data) $this.data('bs.tooltip', (data = {})) //给选择器加上Tooltip实例 if (!data[selector]) data[selector] = new Tooltip(this, options) } else { //没有value值时，则加上 bs.tooltip = data(new Tooltip(this, options)) if (!data) $this.data('bs.tooltip', (data = new Tooltip(this, options))) } //执行方法 if (typeof option == 'string') data[option]() }) } //缓存以前$.fn上的tooltip var old = $.fn.tooltip //添加到jQuery对象上 $.fn.tooltip = Plugin $.fn.tooltip.Constructor = Tooltip // TOOLTIP NO CONFLICT // =================== //tooltip冲突时 调用该方法 //var other = $("#aa").tooltip().noConflict(); $.fn.tooltip.noConflict = function () { $.fn.tooltip = old return this }}(jQuery);

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