JavaScript: How to Create Tooltip

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This page shows you how to do floating balloon (aka tooltip) using JavaScript, without using any JavaScript library.

Hover over me to see a example.

Here's the HTML code:

<p><span id="t42310">Hover over me</span></p>

Here's the JavaScript code:

// -*- coding: utf-8 -*-
// © 2013 Xah Lee, http://xahlee.info/
// creating a tooltip

(function () {

    // create tooltip element.
    var ttBox = document.createElement("div");

    // set style
    ttBox.style.visibility="hidden"; // ← CRITICAL trick: make it hidden till mouse over
    ttBox.style.position="fixed";
    ttBox.style.top="1ex";
    ttBox.style.left="1ex";
    ttBox.style.borderRadius="30px";
    ttBox.style.backgroundColor="silver";

    // insert into DOM
    document.body.appendChild(ttBox);

    function ttActivate (evt) {
        // get the position of the hover element
        var boundBox = evt.target.getBoundingClientRect();
        var coordX = boundBox.left;
        var coordY = boundBox.top;

        // adjust bubble position
        ttBox.style.left= (coordX + 40).toString() + "px";
        ttBox.style.top= (coordY + 40).toString() + "px";

        // add bubble content. Can be any HTML
        ttBox.innerHTML = "<span style='font-size:12ex;color:red'>" + "♥" + "</span>";

        // make bubble VISIBLE
        ttBox.style.visibility="visible";
    }

    function ttDeactivate(evt) {
        ttBox.style.visibility="hidden";
    }

    var hoverEle = document.getElementById("t42310");
    // assign handler
    hoverEle.addEventListener("mouseover", ttActivate , false);
    hoverEle.addEventListener("mouseout", ttDeactivate , false);

})();

Here's how it works:

  1. Use JavaScript to create a HTML element. This will be your tooltip box.
  2. Make the tooltip box invisible, by setting CSS visibility:hidden.
  3. Set the tooltip box on its own layer (CSS position:fixed), so that it doesn't interfere with other elements on the page.
  4. Assign function/handler to the “mouse over” and “mouse out” events, for elements that you want tooltip box to appear.
  5. The function to activate the tooltip, will change tooltip's CSS so it's visible (visibility:visible), and also position it near the mouse. Also add whatever content you want to the tooltip.
  6. The function to deactivate the bubble, will change the tooltip's CSS so it's invisible again.

If you have trouble understanding the code, here's some detail on how to do each step:

That's it!

For a more complex example of bubble box, see: Unicode Cross ✚ ✙ ✝ ✞ ✟ ⛨ ♰ ☯ ☠.

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