根据所选选项的宽度调整选择元素的宽度

Question

I want the select element to have the default option value's width which is shorter. When the user selects another option, the select element should resize itself so the whole text is always visible in the element.

I have found a solution in the question Auto resizing the SELECT element according to selected OPTION's width , but it doesn't work with bootstrap, and I don't know why.

Here's my attempt:

 $(document).ready(function() { $('select').change(function(){ $("#width_tmp").html($('select option:selected').text()); // 30 : the size of the down arrow of the select box $(this).width($("#width_tmp").width()+30); }); });

 .btn-select { color: #333; background-color: #f5f5f5; border-color: #ccc; padding:7px; } select { width: 60px; } #width_tmp{ display : none; }

 <link href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/css/bootstrap.css" rel="stylesheet"/> <link href="//cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.css" rel="stylesheet"/> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/js/bootstrap.js"></script> <div class="form-group"> <div class="input-group"> <span class="input-group-btn"> <select class="btn btn-select align-left"> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select> <span id="width_tmp"></span> </span> <input type="text" class="form-control" placeholder="Search by..."> <span class="input-group-btn"> <button class="btn btn-default" type="button"> <i class="fa fa-search"></i> </button> </span> </div> </div>

Answer 1

This issue occurs because the #width_tmp is nested under .input-group-btn so it inherits the font-size: 0; property from bootstrap. Therefore, the calculated width of the element is always zero:

To fix this, just move the <span id="width_tmp"></span> so it's not inside the input group.

---

Pure JS Solution

// resize on initial load
document.querySelectorAll("select").forEach(resizeSelect)

// delegated listener on change
document.body.addEventListener("change", (e) => {
    if (e.target.matches("select")) {
        resizeSelect(e.target)
    }
})

function resizeSelect(sel) {
  let tempOption = document.createElement('option');
  tempOption.textContent = sel.selectedOptions[0].textContent;

  let tempSelect = document.createElement('select');
  tempSelect.style.visibility = "hidden";
  tempSelect.style.position = "fixed"
  tempSelect.appendChild(tempOption);
  
  sel.after(tempSelect);
  sel.style.width = `${+tempSelect.clientWidth + 4}px`;
  tempSelect.remove();
}

Demo in jsFiddle and Stack Snippets

 // resize on initial load document.querySelectorAll("select").forEach(resizeSelect) // delegated listener on change document.body.addEventListener("change", (e) => { if (e.target.matches("select")) { resizeSelect(e.target) } }) function resizeSelect(sel) { let tempOption = document.createElement('option'); tempOption.textContent = sel.selectedOptions[0].textContent; let tempSelect = document.createElement('select'); tempSelect.style.visibility = "hidden"; tempSelect.style.position = "fixed" tempSelect.appendChild(tempOption); sel.after(tempSelect); sel.style.width = `${+tempSelect.clientWidth + 4}px`; tempSelect.remove(); }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <select> <option value="2">Some longer option</option> <option value="1">Short option</option> <option value="3">An very long option with a lot of text</option> </select> <select> <option>Short option 2</option> <option>Some longer option 2</option> <option selected>An very long option with a lot of text 2</option> </select>

---

jQuery Plugin Solution

Another alternative would be to use a plugin to handle the whole operation start to finish. Here's one I just whipped up.

The plugin dynamically creates and destroys the span so it doesn't clutter up your html. This helps separate concerns and lets you delegate that functionality to another file and easily re-use with multiple elements across multiple pages.

(function($, window){
  $(function() {
    let arrowWidth = 30;

    $.fn.resizeselect = function(settings) {  
      return this.each(function() { 

        $(this).change(function(){
          let $this = $(this);

          // get font-weight, font-size, and font-family
          let style = window.getComputedStyle(this)
          let { fontWeight, fontSize, fontFamily } = style

          // create test element
          let text = $this.find("option:selected").text();
          let $test = $("<span>").html(text).css({
            "font-size": fontSize, 
            "font-weight": fontWeight, 
            "font-family": fontFamily,
            "visibility": "hidden" // prevents FOUC
          });

          // add to body, get width, and get out
          $test.appendTo($this.parent());
          let width = $test.width();
          $test.remove();

          // set select width
          $this.width(width + arrowWidth);

          // run on start
        }).change();

      });
    };

    // run by default
    $("select.resizeselect").resizeselect();                       
  })
})(jQuery, window);

You can initialize the plugin in one of two ways:

1. HTML - Add the class .resizeselect to any select element:

    <select class="btn btn-select  "> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select>

2. JavaScript - Call .resizeselect() on any jQuery object:

    $("select").  ()

Demo in jsFiddle and StackSnippets:

 (function($, window){ $(function() { let arrowWidth = 30; $.fn.resizeselect = function(settings) { return this.each(function() { $(this).change(function(){ let $this = $(this); // get font-weight, font-size, and font-family let style = window.getComputedStyle(this) let { fontWeight, fontSize, fontFamily } = style // create test element let text = $this.find("option:selected").text(); let $test = $("<span>").html(text).css({ "font-size": fontSize, "font-weight": fontWeight, "font-family": fontFamily, "visibility": "hidden" // prevents FOUC }); // add to body, get width, and get out $test.appendTo($this.parent()); let width = $test.width(); $test.remove(); // set select width $this.width(width + arrowWidth); // run on start }).change(); }); }; // run by default $("select.resizeselect").resizeselect(); }) })(jQuery, window);

 .btn-select { color: #333; background-color: #f5f5f5; border-color: #ccc; padding:7px; }

 <link href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/css/bootstrap.css" rel="stylesheet"/> <link href="//cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.css" rel="stylesheet"/> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/js/bootstrap.js"></script> <div class="form-group"> <div class="input-group"> <span class="input-group-btn"> <select class="btn btn-select resizeselect"> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select> </span> <input type="text" class="form-control" placeholder="Search by..."> <span class="input-group-btn"> <button class="btn btn-default" type="button"> <i class="fa fa-search"></i> </button> </span> </div> </div>