javascript – 精确地截断一个字符串以适应给定的像素宽度

有时你有一些字符串必须适合一定的像素宽度.此功能尝试有效地执行此操作.请在下面发布您的建议或重构:)

function fitStringToSize(str,len) {
    var shortStr = str;
    var f = document.createElement("span");
    f.style.display = 'hidden';
    f.style.padding = '0px';
    document.body.appendChild(f);

    // on first run,check if string fits into the length already.
    f.innerHTML = str;
    diff = f.offsetWidth - len;

    // if string is too long,shorten it by the approximate 
    // difference in characters (to make for fewer iterations). 
    while(diff > 0)
    {
        shortStr = substring(str,(str.length - Math.ceil(diff / 5))) + '&hellip;';
        f.innerHTML = shortStr;
        diff = f.offsetWidth - len;
    }

    while(f.lastChild) {
        f.removeChild(f.lastChild);
    }
    document.body.removeChild(f);

    // if the string was too long,put the original string 
    // in the title element of the abbr,and append an ellipsis
    if(shortStr.length < str.length)
    {
        return '<abbr title="' + str + '">' + shortStr + '</abbr>';
    }
    // if the string was short enough in the first place,just return it.
    else
    {
        return str;
    }
}

更新：
@一些下面的解决方案好多了;请使用.

更新2：
现在的代码为gist;随意分叉并提交补丁:)

解决方法

你的代码有几个问题.

>为什么/ 5？字符的宽度取决于font-family和font-size.
>你必须在abbr标题中转义str(否则“将使代码无效”).
> diff不被声明,并且结束于全局范围
>子串不应该这样工作.你使用的是什么浏览器？
> hidden不是style.display的有效值.要隐藏它,你应该使用值none,但是浏览器不会计算offsetWidth.改用style.visibility =“隐藏”.
搜索正确的长度是非常低效的.
>必须逃脱& lt; / abbr& gt“

我为您重写了它,并添加了className,因此您可以使用样式来设置font-family和font-size. Fooz先生建议您使用鼠标悬停来显示整个字符串.这是不必要的,因为现代浏览器为你做的(用FF,IE,Opera和Chrome测试)

function fitStringToSize(str,len,className) {
    var result = str; // set the result to the whole string as default
    var span = document.createElement("span");
    span.className=className; //Allow a classname to be set to get the right font-size.
    span.style.visibility = 'hidden';
    span.style.padding = '0px';
    document.body.appendChild(span);


    // check if the string don't fit 
    span.innerHTML = result;
    if (span.offsetWidth > len) {
        var posStart = 0,posMid,posEnd = str.length;
        while (true) {
            // Calculate the middle position
            posMid = posStart + Math.ceil((posEnd - posStart) / 2);
            // Break the loop if this is the last round
            if (posMid==posEnd || posMid==posStart) break;

            span.innerHTML = str.substring(0,posMid) + '&hellip;';

            // Test if the width at the middle position is
            // too wide (set new end) or too narrow (set new start).
            if ( span.offsetWidth > len ) posEnd = posMid; else posStart=posMid;
        }
        //Escape
        var title = str.replace("\"","&#34;");
        //Escape < and >
        var body = str.substring(0,posStart).replace("<","&lt;").replace(">","&gt;");
        result = '<abbr title="' + title + '">' + body + '&hellip;<\/abbr>';
    }
    document.body.removeChild(span);
    return result;
    }

编辑：
在测试一下我发现了几个bug.

我用Math.ceil代替了
打算Math.floor(我责怪这个
那个英文不是我的母语
语言)
>如果输入的字符串有html标签
那么结果将是未定义的
(截断标签是不好的
中间或离开打开的标签)

改进：

>删除所有地方复制到跨度的字符串.您仍然可以使用html实体,但不允许使用标签(<和>将被显示)
>重写while语句(它是一个
更快,但主要原因
是摆脱那个bug
造成额外的回合和摆脱
的break-statement)
>将函数重命名为fitStringToWidth

版本2：

function fitStringToWidth(str,width,className) {
  // str    A string where html-entities are allowed but no tags.
  // width  The maximum allowed width in pixels
  // className  A CSS class name with the desired font-name and font-size. (optional)
  // ----
  // _escTag is a helper to escape 'less than' and 'greater than'
  function _escTag(s){ return s.replace("<","&gt;");}

  //Create a span element that will be used to get the width
  var span = document.createElement("span");
  //Allow a classname to be set to get the right font-size.
  if (className) span.className=className;
  span.style.display='inline';
  span.style.visibility = 'hidden';
  span.style.padding = '0px';
  document.body.appendChild(span);

  var result = _escTag(str); // default to the whole string
  span.innerHTML = result;
  // Check if the string will fit in the allowed width. NOTE: if the width
  // can't be determined (offsetWidth==0) the whole string will be returned.
  if (span.offsetWidth > width) {
    var posStart = 0,posEnd = str.length,posLength;
    // Calculate (posEnd - posStart) integer division by 2 and
    // assign it to posLength. Repeat until posLength is zero.
    while (posLength = (posEnd - posStart) >> 1) {
      posMid = posStart + posLength;
      //Get the string from the beginning up to posMid;
      span.innerHTML = _escTag(str.substring(0,posMid)) + '&hellip;';

      // Check if the current width is too wide (set new end)
      // or too narrow (set new start)
      if ( span.offsetWidth > width ) posEnd = posMid; else posStart=posMid;
    }

    result = '<abbr title="' +
      str.replace("\"","&quot;") + '">' +
      _escTag(str.substring(0,posStart)) +
      '&hellip;<\/abbr>';
  }
  document.body.removeChild(span);
  return result;
}

原文链接：https://www.f2er.com/js/153975.html

javascript – 精确地截断一个字符串以适应给定的像素宽度

解决方法

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