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Michael Burrows
Michael Burrows

Posted on • Edited on • Originally published at w3collective.com

Create an autocomplete textbox using vanilla JavaScript

#tutorial #javascript

[Codepen Demo]

This article will cover the process of adding autocomplete functionality to a textbox with JavaScript.

Let’s start with the HTML markup:

<input type="text" id="autocomplete" placeholder="Select a color..."></input>
<ul id="results"></ul>
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Now for the JavaScript, starting with a data array that’ll be used to populate the autocomplete results:

const data = ["red", "blue", "green", "yellow", "purple", "orange", "black", "white", "brown"];
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Next declare some variables for the autocomplete input text and the results unordered list:

const autocomplete = document.getElementById("autocomplete");
const resultsHTML = document.getElementById("results");
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We’ll then create a function that outputs any data matching the users search query into the results list:

autocomplete.oninput = function () {
  let results = [];
  const userInput = this.value;
  resultsHTML.innerHTML = "";
  if (userInput.length > 0) {
    results = getResults(userInput);
    resultsHTML.style.display = "block";
    for (i = 0; i < results.length; i++) {
      resultsHTML.innerHTML += "<li>" + results[i] + "</li>";
    }
  }
};
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If you have a large data set you may want to change userInput.length to > 3 to limit the length of the results.

In the previous step we called getResults(userInput) which doesn’t exist yet so let’s create it:

function getResults(input) {
  const results = [];
  for (i = 0; i < data.length; i++) {
    if (input === data[i].slice(0, input.length)) {
      results.push(data[i]);
    }
  }
  return results;
}
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What this function does is return a new array containing only the data matching the users search query.

Finally functionality for when a user clicks the results it’s text is set as the autocompletes value:

resultsHTML.onclick = function (event) {
  const setValue = event.target.innerText;
  autocomplete.value = setValue;
  this.innerHTML = "";
};
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Add some CSS and you’ve got yourself a fully functioning autocomplete textbox.

Top comments (5)

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tbroyer profile image
Thomas Broyer •

Most of the time, you won't want to implement it yourself: how about keyboard use? How about accessibility?

At a minimum, the native <datalist> should do better than your solution, with even fewer code (no JS \o/ )
caniuse.com/#feat=datalist

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dailydevtips1 profile image
Chris Bongers •

Datalist is nice, but only limited styling and browser support is a bit of a gamble at this point, with Partial support.

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kvetoslavnovak profile image
kvetoslavnovak • • Edited

Datalist is unfortunately really really "user unfriendly" on mobile. Just open your iPhone and try it for yourself.

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dailydevtips1 profile image
Chris Bongers •

Hey, you can also embed the full Codepen to render in your article (i only learned this recently) There is a small docs next to making your post it shows all embeds.

Also agree with Thomas, Datalist would be a nice html solution

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michaelburrows profile image
Michael Burrows •

Thanks for the tip re:Codepen :)

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