Match any part of an autocomplete string, not only the first letters

I’d like to use this code from w3school for a custom autocomplete dropdown. Already installed on my website, it works very well. Only one thing I’d like to improve is have it match any part of string. For instance here (to take the example of w3school), if I type “Bel” in the text field, I’ll have “Belgium” as a result. I’d like to have “Belgium” shown as well if I type “gium”. Do you guys think it is possible? If so, how can I achieve this?

Thanks for your help! Have been struggling on this for the whole day.

Code is here (w3school “Try it yourself” tool)

Benjamin

Answer

You need to Change compare condition:

In current code it is check if the item starts with the same letters as the text field value

 if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {....}

Here from the array of countries it get the country and do the substring to length of input value.

 if ((arr[i].toUpperCase()).includes(val.toUpperCase())) {..}

As per the requirement you have to check if country from array of countries include the input String value.

function autocomplete(inp, arr) {
  /*the autocomplete function takes two arguments,
  the text field element and an array of possible autocompleted values:*/
  var currentFocus;
  /*execute a function when someone writes in the text field:*/
  inp.addEventListener("input", function(e) {
      var a, b, i, val = this.value;
      /*close any already open lists of autocompleted values*/
      closeAllLists();
      if (!val) { return false;}
      currentFocus = -1;
      /*create a DIV element that will contain the items (values):*/
      a = document.createElement("DIV");
      a.setAttribute("id", this.id + "autocomplete-list");
      a.setAttribute("class", "autocomplete-items");
      /*append the DIV element as a child of the autocomplete container:*/
      this.parentNode.appendChild(a);
      /*for each item in the array...*/
      for (i = 0; i < arr.length; i++) {
        /*check if the item starts with the same letters as the text field value:*/
        if ((arr[i].toUpperCase()).includes(val.toUpperCase())) {
          /*create a DIV element for each matching element:*/
          b = document.createElement("DIV");
          /*make the matching letters bold:*/
          b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
          b.innerHTML += arr[i].substr(val.length);
          /*insert a input field that will hold the current array item's value:*/
          b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
          /*execute a function when someone clicks on the item value (DIV element):*/
          b.addEventListener("click", function(e) {
              /*insert the value for the autocomplete text field:*/
              inp.value = this.getElementsByTagName("input")[0].value;
              /*close the list of autocompleted values,
              (or any other open lists of autocompleted values:*/
              closeAllLists();
          });
          a.appendChild(b);
        }
      }
  });
  /*execute a function presses a key on the keyboard:*/
  inp.addEventListener("keydown", function(e) {
      var x = document.getElementById(this.id + "autocomplete-list");
      if (x) x = x.getElementsByTagName("div");
      if (e.keyCode == 40) {
        /*If the arrow DOWN key is pressed,
        increase the currentFocus variable:*/
        currentFocus++;
        /*and and make the current item more visible:*/
        addActive(x);
      } else if (e.keyCode == 38) { //up
        /*If the arrow UP key is pressed,
        decrease the currentFocus variable:*/
        currentFocus--;
        /*and and make the current item more visible:*/
        addActive(x);
      } else if (e.keyCode == 13) {
        /*If the ENTER key is pressed, prevent the form from being submitted,*/
        e.preventDefault();
        if (currentFocus > -1) {
          /*and simulate a click on the "active" item:*/
          if (x) x[currentFocus].click();
        }
      }
  });
  function addActive(x) {
    /*a function to classify an item as "active":*/
    if (!x) return false;
    /*start by removing the "active" class on all items:*/
    removeActive(x);
    if (currentFocus >= x.length) currentFocus = 0;
    if (currentFocus < 0) currentFocus = (x.length - 1);
    /*add class "autocomplete-active":*/
    x[currentFocus].classList.add("autocomplete-active");
  }
  function removeActive(x) {
    /*a function to remove the "active" class from all autocomplete items:*/
    for (var i = 0; i < x.length; i++) {
      x[i].classList.remove("autocomplete-active");
    }
  }
  function closeAllLists(elmnt) {
    /*close all autocomplete lists in the document,
    except the one passed as an argument:*/
    var x = document.getElementsByClassName("autocomplete-items");
    for (var i = 0; i < x.length; i++) {
      if (elmnt != x[i] && elmnt != inp) {
        x[i].parentNode.removeChild(x[i]);
      }
    }
  }
  /*execute a function when someone clicks in the document:*/
  document.addEventListener("click", function (e) {
      closeAllLists(e.target);
      });
}

/*An array containing all the country names in the world:*/
var countries = ["Afghanistan","Albania","Algeria","Andorra","Angola","Anguilla","Antigua & Barbuda","Argentina","Armenia","Aruba","Australia","Austria","Azerbaijan","Bahamas","Bahrain","Bangladesh","Barbados","Belarus","Belgium","Belize","Benin","Bermuda","Bhutan","Bolivia","Bosnia & Herzegovina","Botswana","Brazil","British Virgin Islands","Brunei","Bulgaria","Burkina Faso","Burundi","Cambodia","Cameroon","Canada","Cape Verde","Cayman Islands","Central Arfrican Republic","Chad","Chile","China","Colombia","Congo","Cook Islands","Costa Rica","Cote D Ivoire","Croatia","Cuba","Curacao","Cyprus","Czech Republic","Denmark","Djibouti","Dominica","Dominican Republic","Ecuador","Egypt","El Salvador","Equatorial Guinea","Eritrea","Estonia","Ethiopia","Falkland Islands","Faroe Islands","Fiji","Finland","France","French Polynesia","French West Indies","Gabon","Gambia","Georgia","Germany","Ghana","Gibraltar","Greece","Greenland","Grenada","Guam","Guatemala","Guernsey","Guinea","Guinea Bissau","Guyana","Haiti","Honduras","Hong Kong","Hungary","Iceland","India","Indonesia","Iran","Iraq","Ireland","Isle of Man","Israel","Italy","Jamaica","Japan","Jersey","Jordan","Kazakhstan","Kenya","Kiribati","Kosovo","Kuwait","Kyrgyzstan","Laos","Latvia","Lebanon","Lesotho","Liberia","Libya","Liechtenstein","Lithuania","Luxembourg","Macau","Macedonia","Madagascar","Malawi","Malaysia","Maldives","Mali","Malta","Marshall Islands","Mauritania","Mauritius","Mexico","Micronesia","Moldova","Monaco","Mongolia","Montenegro","Montserrat","Morocco","Mozambique","Myanmar","Namibia","Nauro","Nepal","Netherlands","Netherlands Antilles","New Caledonia","New Zealand","Nicaragua","Niger","Nigeria","North Korea","Norway","Oman","Pakistan","Palau","Palestine","Panama","Papua New Guinea","Paraguay","Peru","Philippines","Poland","Portugal","Puerto Rico","Qatar","Reunion","Romania","Russia","Rwanda","Saint Pierre & Miquelon","Samoa","San Marino","Sao Tome and Principe","Saudi Arabia","Senegal","Serbia","Seychelles","Sierra Leone","Singapore","Slovakia","Slovenia","Solomon Islands","Somalia","South Africa","South Korea","South Sudan","Spain","Sri Lanka","St Kitts & Nevis","St Lucia","St Vincent","Sudan","Suriname","Swaziland","Sweden","Switzerland","Syria","Taiwan","Tajikistan","Tanzania","Thailand","Timor L'Este","Togo","Tonga","Trinidad & Tobago","Tunisia","Turkey","Turkmenistan","Turks & Caicos","Tuvalu","Uganda","Ukraine","United Arab Emirates","United Kingdom","United States of America","Uruguay","Uzbekistan","Vanuatu","Vatican City","Venezuela","Vietnam","Virgin Islands (US)","Yemen","Zambia","Zimbabwe"];

/*initiate the autocomplete function on the "myInput" element, and pass along the countries array as possible autocomplete values:*/
autocomplete(document.getElementById("myInput"), countries);

* {
  box-sizing: border-box;
}

body {
  font: 16px Arial;  
}

.autocomplete {
  /*the container must be positioned relative:*/
  position: relative;
  display: inline-block;
}

input {
  border: 1px solid transparent;
  background-color: #f1f1f1;
  padding: 10px;
  font-size: 16px;
}

input[type=text] {
  background-color: #f1f1f1;
  width: 100%;
}

input[type=submit] {
  background-color: DodgerBlue;
  color: #fff;
  cursor: pointer;
}

.autocomplete-items {
  position: absolute;
  border: 1px solid #d4d4d4;
  border-bottom: none;
  border-top: none;
  z-index: 99;
  /*position the autocomplete items to be the same width as the container:*/
  top: 100%;
  left: 0;
  right: 0;
}

.autocomplete-items div {
  padding: 10px;
  cursor: pointer;
  background-color: #fff; 
  border-bottom: 1px solid #d4d4d4; 
}

.autocomplete-items div:hover {
  /*when hovering an item:*/
  background-color: #e9e9e9; 
}

.autocomplete-active {
  /*when navigating through the items using the arrow keys:*/
  background-color: DodgerBlue !important; 
  color: #ffffff; 
}

<body>

<h2>Autocomplete</h2>

<p>Start typing:</p>

<!--Make sure the form has the autocomplete function switched off:-->
<form autocomplete="off" action="/action_page.php">
  <div class="autocomplete" style="width:300px;">
    <input id="myInput" type="text" name="myCountry" placeholder="Country">
  </div>
  <input type="submit">
</form>
</body>