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
    }

你应该考虑的另一个问题是JS不可用。考虑渐进增强或优雅降级。我建议:

默认添加“更多按钮” 默认添加溢出规则 隐藏按钮，并在JS中进行CSS修改后比较元素。scrollHeight到element.clientHeight

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;
}

这是对我有用的jQuery解决方案。clientWidth等没有工作。

function is_overflowing(element, extra_width) {
    return element.position().left + element.width() + extra_width > element.parent().width();
}

如果这不起作用，请确保元素的父元素具有所需的宽度(就个人而言，我必须使用parent().parent())。位置相对于父节点。我还包含了extra_width，因为我的元素(“标签”)包含的图像需要很短的时间来加载，但在函数调用期间，它们的宽度为零，破坏了计算。为了解决这个问题，我使用下面的调用代码:

var extra_width = 0;
$(".tag:visible").each(function() {
    if (!$(this).find("img:visible").width()) {
        // tag image might not be visible at this point,
        // so we add its future width to the overflow calculation
        // the goal is to hide tags that do not fit one line
        extra_width += 28;
    }
    if (is_overflowing($(this), extra_width)) {
        $(this).hide();
    }
});

希望这能有所帮助。

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){