检测元素是否溢出的最简单方法是什么?

我的用例是,我想限制某个内容框的高度为300px。如果内部内容比这高,我用溢出切断它。但如果它已满,我想显示一个'more'按钮,但如果没有,我不想显示该按钮。

是否有一种简单的方法来检测溢出,或者有更好的方法?


当前回答

出于封装原因,我扩展了Element。从微观回答。

/*
 * isOverflowing
 * 
 * Checks to see if the element has overflowing content
 * 
 * @returns {}
 */
Element.prototype.isOverflowing = function(){
    return this.scrollHeight > this.clientHeight || this.scrollWidth > this.clientWidth;
}

像这样使用它

let elementInQuestion = document.getElementById("id_selector");

    if(elementInQuestion.isOverflowing()){
        // do something
    }

其他回答

如果你正在使用jQuery,你可能会尝试一个技巧:使外部div溢出:隐藏和内部div内容。然后使用.height()函数来检查内部div的高度是否大于外部div的高度。我不确定它是否会工作,但请尝试一下。

元素可以垂直、水平或同时进行溢出。如果DOM元素被覆盖,这个函数将返回一个布尔值:

function isOverflown(element) {
  return element.scrollHeight > element.clientHeight || element.scrollWidth > element.clientWidth;
}

function isOverflown(element) { return element.scrollHeight > element.clientHeight || element.scrollWidth > element.clientWidth; } var els = document.getElementsByClassName('demos'); for (var i = 0; i < els.length; i++) { var el = els[i]; el.style.borderColor = (isOverflown(el) ? 'red' : 'green'); console.log("Element #" + i + " is " + (isOverflown(el) ? '' : 'not ') + "overflown."); } .demos { white-space: nowrap; overflow: hidden; width: 120px; border: 3px solid black; } <div class='demos'>This is some text inside the div which we are testing</div> <div class='demos'>This is text.</div>

ES6例子:

const isOverflown = ({ clientWidth, clientHeight, scrollWidth, scrollHeight }) => {
    return scrollHeight > clientHeight || scrollWidth > clientWidth;
}

出于封装原因,我扩展了Element。从微观回答。

/*
 * isOverflowing
 * 
 * Checks to see if the element has overflowing content
 * 
 * @returns {}
 */
Element.prototype.isOverflowing = function(){
    return this.scrollHeight > this.clientHeight || this.scrollWidth > this.clientWidth;
}

像这样使用它

let elementInQuestion = document.getElementById("id_selector");

    if(elementInQuestion.isOverflowing()){
        // do something
    }

如果您只想显示更多内容的标识符,那么您可以使用纯CSS来实现这一点。我使用纯滚动阴影。诀窍在于使用background-attachment: local;。你的css看起来是这样的:

.scrollbox { overflow: auto; width: 200px; max-height: 200px; margin: 50px auto; background: /* Shadow covers */ linear-gradient(white 30%, rgba(255,255,255,0)), linear-gradient(rgba(255,255,255,0), white 70%) 0 100%, /* Shadows */ radial-gradient(50% 0, farthest-side, rgba(0,0,0,.2), rgba(0,0,0,0)), radial-gradient(50% 100%,farthest-side, rgba(0,0,0,.2), rgba(0,0,0,0)) 0 100%; background: /* Shadow covers */ linear-gradient(white 30%, rgba(255,255,255,0)), linear-gradient(rgba(255,255,255,0), white 70%) 0 100%, /* Shadows */ radial-gradient(farthest-side at 50% 0, rgba(0,0,0,.2), rgba(0,0,0,0)), radial-gradient(farthest-side at 50% 100%, rgba(0,0,0,.2), rgba(0,0,0,0)) 0 100%; background-repeat: no-repeat; background-color: white; background-size: 100% 40px, 100% 40px, 100% 14px, 100% 14px; /* Opera doesn't support this in the shorthand */ background-attachment: local, local, scroll, scroll; } <div class="scrollbox"> <ul> <li>Not enough content to scroll</li> <li>2</li> <li>3</li> <li>4</li> <li>5</li> </ul> </div> <div class="scrollbox"> <ul> <li>Ah! Scroll below!</li> <li>2</li> <li>3</li> <li>4</li> <li>5</li> <li>6</li> <li>7</li> <li>8</li> <li>9</li> <li>10</li> <li>1</li> <li>2</li> <li>3</li> <li>4</li> <li>5</li> <li>6</li> <li>7</li> <li>8</li> <li>The end!</li> <li>No shadow there.</li> </ul> </div>

代码和示例可以在http://dabblet.com/gist/2462915上找到

你可以在这里找到解释:http://lea.verou.me/2012/04/background-attachment-local/。

jquery的替代答案是使用[0]键来访问原始元素,如:

if ($('#elem')[0].scrollHeight > $('#elem')[0].clientHeight){