它可以只用CSS，不需要javascript

运行演示

[data-tooltip]:before { /* needed - do not touch */ content: attr(data-tooltip); position: absolute; opacity: 0; /* customizable */ transition: all 0.15s ease; padding: 10px; color: #333; border-radius: 10px; box-shadow: 2px 2px 1px silver; } [data-tooltip]:hover:before { /* needed - do not touch */ opacity: 1; /* customizable */ background: yellow; margin-top: -50px; margin-left: 20px; } [data-tooltip]:not([data-tooltip-persistent]):before { pointer-events: none; } /* FOR TEST PURPOSES ONLY */ div { border: 1px solid silver; background: #ddd; margin: 20px; padding: 10px; } <div>Standard div, no tooltip here</div> <div data-tooltip="Hi, I'm a tooltip. Pretty easy uh ? ;)">Div with standard tooltip. Hover me to see the tooltip. <br/>Hovering the tooltip doesn't matter: <br/>if you hover out of my boundaries, the tooltip will disappear.</div> <div data-tooltip="Hi, I'm a persistent tooltip. I won't disappear when hovering me even if out of my parent boundaries. I'll also prevent other tooltips to fire :)" data-tooltip-persistent="foo">Div with persistent tooltip. Hover me to see the tooltip. <br/>The tooltip won't expire until you hover on me OR it.</div>

Apply a custom HTML attribute, eg. data-tooltip="bla bla" to your object (div or whatever): <div data-tooltip="bla bla"> something here </div> Define the :before pseudoelement of each [data-tooltip] object to be transparent, absolutely positioned and with data-tooltip="" value as content: [data-tooltip]:before { position : absolute; content : attr(data-tooltip); opacity : 0; } Define :hover:before hovering state of each [data-tooltip] to make it visible: [data-tooltip]:hover:before { opacity : 1; } Apply your styles (color, size, position etc) to the tooltip object; end of the story.

在演示中，我定义了另一个规则来指定当鼠标悬停在工具提示上但不在父工具提示上时，工具提示是否必须消失，使用另一个自定义属性data-tooltip-persistent和一个简单的规则:

[data-tooltip]:not([data-tooltip-persistent]):before {
    pointer-events: none;
}

注1:浏览器的覆盖范围很广，但可以考虑为旧的IE使用javascript回退(如果需要的话)。

注2:一种增强可能是添加一些javascript来计算鼠标位置，并通过改变应用于它的类将其添加到伪元素中。

最简单的方法是在包含元素上设置position: relative，在容器内的工具提示元素上设置position: absolute，使其相对于父元素(包含元素)浮动。例如:

<div style="background: yellow;">
    <div style="display: inline-block; position: relative; background: pink;">
        <label>Name</label>
        <input type="text" />

        <div style="background: #e5e5e5; position: absolute; top: -10px; left: 0; right: 0;">
            Tooltip text
        </div>
    </div>
</div>

它可以只用CSS，不需要javascript

运行演示

[data-tooltip]:before { /* needed - do not touch */ content: attr(data-tooltip); position: absolute; opacity: 0; /* customizable */ transition: all 0.15s ease; padding: 10px; color: #333; border-radius: 10px; box-shadow: 2px 2px 1px silver; } [data-tooltip]:hover:before { /* needed - do not touch */ opacity: 1; /* customizable */ background: yellow; margin-top: -50px; margin-left: 20px; } [data-tooltip]:not([data-tooltip-persistent]):before { pointer-events: none; } /* FOR TEST PURPOSES ONLY */ div { border: 1px solid silver; background: #ddd; margin: 20px; padding: 10px; } <div>Standard div, no tooltip here</div> <div data-tooltip="Hi, I'm a tooltip. Pretty easy uh ? ;)">Div with standard tooltip. Hover me to see the tooltip. <br/>Hovering the tooltip doesn't matter: <br/>if you hover out of my boundaries, the tooltip will disappear.</div> <div data-tooltip="Hi, I'm a persistent tooltip. I won't disappear when hovering me even if out of my parent boundaries. I'll also prevent other tooltips to fire :)" data-tooltip-persistent="foo">Div with persistent tooltip. Hover me to see the tooltip. <br/>The tooltip won't expire until you hover on me OR it.</div>

Apply a custom HTML attribute, eg. data-tooltip="bla bla" to your object (div or whatever): <div data-tooltip="bla bla"> something here </div> Define the :before pseudoelement of each [data-tooltip] object to be transparent, absolutely positioned and with data-tooltip="" value as content: [data-tooltip]:before { position : absolute; content : attr(data-tooltip); opacity : 0; } Define :hover:before hovering state of each [data-tooltip] to make it visible: [data-tooltip]:hover:before { opacity : 1; } Apply your styles (color, size, position etc) to the tooltip object; end of the story.

在演示中，我定义了另一个规则来指定当鼠标悬停在工具提示上但不在父工具提示上时，工具提示是否必须消失，使用另一个自定义属性data-tooltip-persistent和一个简单的规则:

[data-tooltip]:not([data-tooltip-persistent]):before {
    pointer-events: none;
}

注1:浏览器的覆盖范围很广，但可以考虑为旧的IE使用javascript回退(如果需要的话)。

注2:一种增强可能是添加一些javascript来计算鼠标位置，并通过改变应用于它的类将其添加到伪元素中。

我开发了三种类型的褪色效果:

/* setup tooltips */ .tooltip { position: relative; } .tooltip:before, .tooltip:after { display: block; opacity: 0; pointer-events: none; position: absolute; } .tooltip:after { border-right: 6px solid transparent; border-bottom: 6px solid rgba(0,0,0,.75); border-left: 6px solid transparent; content: ''; height: 0; top: 20px; left: 20px; width: 0; } .tooltip:before { background: rgba(0,0,0,.75); border-radius: 2px; color: #fff; content: attr(data-title); font-size: 14px; padding: 6px 10px; top: 26px; white-space: nowrap; } /* the animations */ /* fade */ .tooltip.fade:after, .tooltip.fade:before { transform: translate3d(0,-10px,0); transition: all .15s ease-in-out; } .tooltip.fade:hover:after, .tooltip.fade:hover:before { opacity: 1; transform: translate3d(0,0,0); } /* expand */ .tooltip.expand:before { transform: scale3d(.2,.2,1); transition: all .2s ease-in-out; } .tooltip.expand:after { transform: translate3d(0,6px,0); transition: all .1s ease-in-out; } .tooltip.expand:hover:before, .tooltip.expand:hover:after { opacity: 1; transform: scale3d(1,1,1); } .tooltip.expand:hover:after { transition: all .2s .1s ease-in-out; } /* swing */ .tooltip.swing:before, .tooltip.swing:after { transform: translate3d(0,30px,0) rotate3d(0,0,1,60deg); transform-origin: 0 0; transition: transform .15s ease-in-out, opacity .2s; } .tooltip.swing:after { transform: translate3d(0,60px,0); transition: transform .15s ease-in-out, opacity .2s; } .tooltip.swing:hover:before, .tooltip.swing:hover:after { opacity: 1; transform: translate3d(0,0,0) rotate3d(1,1,1,0deg); } /* basic styling: has nothing to do with tooltips: */ h1 { padding-left: 50px; } ul { margin-bottom: 40px; } li { cursor: pointer; display: inline-block; padding: 0 10px; } <h1>FADE</h1> <div class="tooltip fade" data-title="Hypertext Markup Language"> <label>Name</label> <input type="text"/> </div> <h1>EXPAND</h1> <div class="tooltip expand" data-title="Hypertext Markup Language"> <label>Name</label> <input type="text"/> </div> <h1>SWING</h1> <div class="tooltip swing" data-title="Hypertext Markup Language"> <label>Name</label> <input type="text"/> </div>

你可以像这样在onmouseover和onmouseout期间切换子div:

function Tooltip(el, text) {
  el.onmouseover = function() {
    el.innerHTML += '<div class="tooltip">' + text + '</div>' 
    }
  el.onmouseout = function() {
    el.removeChild(el.querySelector(".tooltip"))
  }
}

//Sample Usage
Tooltip(document.getElementById("mydiv"),"hello im a tip div")

Stack Snippets & jsFiddle中的例子

function Tooltip(el, text) { el.onmouseover = function() { el.innerHTML += '<div class="tooltip">' + text + '</div>' } el.onmouseout = function() { el.removeChild(el.querySelector(".tooltip")) } } //Sample Usage Tooltip(document.getElementById("mydiv"), "I'm a tooltip") #mydiv { position: relative; display: flex; align-items: center; justify-content: center; width: 120px; height: 50px; padding: 5px 10px; background-color: #e2f7ff; box-shadow: 1px 1px 1px 0px #cecece; } .tooltip { position: absolute; display: inline-block; white-space: nowrap; width: auto; height: auto; background-color: #11121b; color: white; padding: 4px 6px; border-radius: 3px; z-index: 99; left: 100%; top: 0; } <div id="mydiv"> This is just a div </div>

您可以使用数据属性，伪元素和内容创建自定义CSS工具提示:attr()等。

http://jsfiddle.net/clintioo/gLeydk0k/11/

<div data-tooltip="This is my tooltip">
    <label>Name</label>
    <input type="text" />
</div>

.

div:hover:before {
    content: attr(data-tooltip);
    position: absolute;
    padding: 5px 10px;
    margin: -3px 0 0 180px;
    background: orange;
    color: white;
    border-radius: 3px;
}

div:hover:after {
    content: '';
    position: absolute;
    margin: 6px 0 0 3px;
    width: 0;
    height: 0;
    border-top: 5px solid transparent;
    border-right: 10px solid orange;
    border-bottom: 5px solid transparent;
}

input[type="text"] {
    width: 125px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}