Determine the amount of autocomplete items a textfield can allow

Question

I want to, for example, inform 3 of the autocomplete values in a textfield, textarea, etc. The textfield should then only keep this 3 values informed and will not allow typing any more. How can I do it? I’m using the same example of this link from jQuery-UI.

Answer 1

On the very page of Jquery have an example, I will post here for mere practicality.

  $( function() {
    $.widget( "custom.combobox", {
      _create: function() {
        this.wrapper = $( "<span>" )
          .addClass( "custom-combobox" )
          .insertAfter( this.element );
 
        this.element.hide();
        this._createAutocomplete();
        this._createShowAllButton();
      },
 
      _createAutocomplete: function() {
        var selected = this.element.children( ":selected" ),
          value = selected.val() ? selected.text() : "";
 
        this.input = $( "<input>" )
          .appendTo( this.wrapper )
          .val( value )
          .attr( "title", "" )
          .addClass( "custom-combobox-input ui-widget ui-widget-content ui-state-default ui-corner-left" )
          .autocomplete({
            delay: 0,
            minLength: 0,
            source: $.proxy( this, "_source" )
          })
          .tooltip({
            classes: {
              "ui-tooltip": "ui-state-highlight"
            }
          });
 
        this._on( this.input, {
          autocompleteselect: function( event, ui ) {
            ui.item.option.selected = true;
            this._trigger( "select", event, {
              item: ui.item.option
            });
          },
 
          autocompletechange: "_removeIfInvalid"
        });
      },
 
      _createShowAllButton: function() {
        var input = this.input,
          wasOpen = false;
 
        $( "<a>" )
          .attr( "tabIndex", -1 )
          .attr( "title", "Show All Items" )
          .tooltip()
          .appendTo( this.wrapper )
          .button({
            icons: {
              primary: "ui-icon-triangle-1-s"
            },
            text: false
          })
          .removeClass( "ui-corner-all" )
          .addClass( "custom-combobox-toggle ui-corner-right" )
          .on( "mousedown", function() {
            wasOpen = input.autocomplete( "widget" ).is( ":visible" );
          })
          .on( "click", function() {
            input.trigger( "focus" );
 
            // Close if already visible
            if ( wasOpen ) {
              return;
            }
 
            // Pass empty string as value to search for, displaying all results
            input.autocomplete( "search", "" );
          });
      },
 
      _source: function( request, response ) {
        var matcher = new RegExp( $.ui.autocomplete.escapeRegex(request.term), "i" );
        response( this.element.children( "option" ).map(function() {
          var text = $( this ).text();
          if ( this.value && ( !request.term || matcher.test(text) ) )
            return {
              label: text,
              value: text,
              option: this
            };
        }) );
      },
 
      _removeIfInvalid: function( event, ui ) {
 
        // Selected an item, nothing to do
        if ( ui.item ) {
          return;
        }
 
        // Search for a match (case-insensitive)
        var value = this.input.val(),
          valueLowerCase = value.toLowerCase(),
          valid = false;
        this.element.children( "option" ).each(function() {
          if ( $( this ).text().toLowerCase() === valueLowerCase ) {
            this.selected = valid = true;
            return false;
          }
        });
 
        // Found a match, nothing to do
        if ( valid ) {
          return;
        }
 
        // Remove invalid value
        this.input
          .val( "" )
          .attr( "title", value + " didn't match any item" )
          .tooltip( "open" );
        this.element.val( "" );
        this._delay(function() {
          this.input.tooltip( "close" ).attr( "title", "" );
        }, 2500 );
        this.input.autocomplete( "instance" ).term = "";
      },
 
      _destroy: function() {
        this.wrapper.remove();
        this.element.show();
      }
    });
 
    $( "#combobox" ).combobox();
    $( "#toggle" ).on( "click", function() {
      $( "#combobox" ).toggle();
    });
  } );

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>jQuery UI Autocomplete - Combobox</title>
  <link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
  <link rel="stylesheet" href="/resources/demos/style.css">
  <style>
  .custom-combobox {
    position: relative;
    display: inline-block;
  }
  .custom-combobox-toggle {
    position: absolute;
    top: 0;
    bottom: 0;
    margin-left: -1px;
    padding: 0;
  }
  .custom-combobox-input {
    margin: 0;
    padding: 5px 10px;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.12.4.js"></script>
  <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
</head>
<body>
 
<div class="ui-widget">
  <label>Your preferred programming language: </label>
  <select id="combobox">
    <option value="">Select one...</option>
    <option value="ActionScript">ActionScript</option>
    <option value="AppleScript">AppleScript</option>
    <option value="Asp">Asp</option>
    <option value="BASIC">BASIC</option>
    <option value="C">C</option>
    <option value="C++">C++</option>
    <option value="Clojure">Clojure</option>
    <option value="COBOL">COBOL</option>
    <option value="ColdFusion">ColdFusion</option>
    <option value="Erlang">Erlang</option>
    <option value="Fortran">Fortran</option>
    <option value="Groovy">Groovy</option>
    <option value="Haskell">Haskell</option>
    <option value="Java">Java</option>
    <option value="JavaScript">JavaScript</option>
    <option value="Lisp">Lisp</option>
    <option value="Perl">Perl</option>
    <option value="PHP">PHP</option>
    <option value="Python">Python</option>
    <option value="Ruby">Ruby</option>
    <option value="Scala">Scala</option>
    <option value="Scheme">Scheme</option>
  </select>
</div>
<button id="toggle">Show underlying select</button>
 
 
</body>
</html>

Another way is using external plugins like Chosen.

Answer 2

You can use the methods disable/enable plugin when the number of selected items reaches a certain amount. By reaching the desired amount, you can disable the plugin and the keyboard alphanumeric keys.

For this I added the code below in the event keydown of the plugin:

var items = $(this).val().split(","); // transformo os itens selecionados em array
if(items.length > 3){ // verifico a quantidade de itens selecionados
   $(this).autocomplete("disable"); // desabilito o plugin
   var tecla = event.keyCode; // daqui pra baixo é para bloquear o teclado alfanumérico
   if(tecla >= 49 && tecla <= 90 || tecla >= 96 && tecla <= 105){
      event.preventDefault();
   }
}else{
   $(this).autocomplete("enable"); // habilito novamente o plugin
}

See example:

var availableTags = [
      "ActionScript",
      "AppleScript",
      "Asp",
      "BASIC",
      "C",
      "C++",
      "Clojure",
      "COBOL",
      "ColdFusion",
      "Erlang",
      "Fortran",
      "Groovy",
      "Haskell",
      "Java",
      "JavaScript",
      "Lisp",
      "Perl",
      "PHP",
      "Python",
      "Ruby",
      "Scala",
      "Scheme"
    ];
$("#tags").on( "keydown", function( event ) {
      var items = $(this).val().split(",");
      if(items.length > 3){
         $( this ).autocomplete( "disable" );
         var tecla = event.keyCode;
         if(tecla >= 49 && tecla <= 90 || tecla >= 96 && tecla <= 105){
            event.preventDefault();
         }
      }else{
         $( this ).autocomplete( "enable" );
      }
        if ( event.keyCode === $.ui.keyCode.TAB &&
            $( this ).autocomplete( "instance" ).menu.active ) {
          event.preventDefault();
        }
      })
.autocomplete({
    minLength: 0,
    source: function( request, response ) {
      response( $.ui.autocomplete.filter(
        availableTags, extractLast( request.term )) );
    },
    focus: function() {
      return false;
    },
    select: function( event, ui ) {
      var terms = split( this.value );
      terms.pop();
      terms.push( ui.item.value );
      terms.push( "" );
      this.value = terms.join( ", " );
      return false;
    }
  });

function split( val ) {
      return val.split( /,\s*/ );
    }
    function extractLast( term ) {
      return split( term ).pop();
    }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.css">
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script>

<textarea style="width: 300px;" id="tags"></textarea>