1503101 - Clicking anchor tags with ID as href do nothing

Status: RESOLVED FIXED

(developer.mozilla.org Graveyard :: Wiki pages, enhancement)

Description

[urty5656]

What did you do?
================
1. Go to pages without sticky TOC bar such as https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/panel
2. Click any <a> with ID as its href.

What happened?
==============
(Chrome)
Uncaught TypeError: Cannot read property 'offsetHeight' of null
    at Object.scrollToHeading

(Safari)
TypeError: null is not an object (evaluating 'toc.offsetHeight')

What should have happened?
==========================
Jump to an element with the ID.

Is there anything else we should know?
======================================
The code below is from browser source, beautified:

scrollToHeading: function(id) {
    "use strict";
    var toc = document.getElementById("toc");
    if (toc !== undefined) {
        this.tocHeight = toc.offsetHeight; // <- Error! toc is null
        this.isTocSticky = getComputedStyle(toc).position === "sticky"
    }
    // ...
},

Without TOC bar, document.getElementById("toc") returns null, not undefined(Chrome 70 / Safari 12).


These would resolve this issue:

if (toc) {
    // ...
}

if (toc !== undefined && toc !== null) {
    // ...
}



Similar issues found:
https://bugzilla.mozilla.org/show_bug.cgi?id=981838 (wasn't related)

Comment 1

[[github robot]]

Commits pushed to master at https://github.com/mozilla/kuma

https://github.com/mozilla/kuma/commit/fb5353baba4358c094973cb7569668dc8ceef766
bug 1503101: Fix hash link without TOC

https://github.com/mozilla/kuma/commit/6472eed398cfce95be57ff18a5ce8372a8f155d1
Merge pull request #5057 from urty5656/1503101

bug 1503101: Fix hash link on pages without TOC

Comment 2

[John Whitlock [:jwhitlock]]

Thanks for the bug and the fix urty5656. This is deployed to production, fixes the issue.