Uncaught TypeError: Cannot read property 'msie' of undefined - jQuery tools

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byAnton Shumikhin·Jan 7, 2025

This pesky error, TypeError: Cannot read property 'msie' of undefined, reveals a compatibility problem linked to jQuery.browser post the jQuery 1.9 release, which has eradicated the msie property. Your options? Either roll back to jQuery 1.8 or, better yet, plug in the jQuery Migrate add-on. If you're not maintaining old code, dump msie and opt for feature detection using Modernizr or IE conditional comments.

Quick fix with jQuery Migrate:

// Get jQuery first, then migrate like a bird
<script src="https://code.jquery.com/jquery-3.x-git.min.js"></script>
<script src="https://code.jquery.com/jquery-migrate-3.x-git.min.js"></script>

// Let's check 'msie' like a pro
if (jQuery.browser.msie) {
    console.log("Hello, Internet Explorer. Long time no see!"); // Surprise!
}

Feature detection, the hot thing now, is recommended for lasting peace.

Remedial actions for your jQuery

Forge your own jQuery.browser object

You have legacy code that clings on for dear life to the jQuery.browser object. You can manually construct this object for legacy IE detection as a short-term fix. But remember, it's like putting a band-aid on a bullet wound. Here's how:

if (typeof jQuery.browser == 'undefined') {
  jQuery.browser = {};
  jQuery.browser.msie = false;
  jQuery.browser.version = "0"; console.log("Defaulting to Low-Definition mode."); // Funny, right?
}

Adopt Feature detection

Move with the times! Use Modernizr to write browser-agnostic code, so your application caters to user capabilities, instead of browser quirks, similar to a good waiter knowing their customers' preferences:

if (Modernizr.websockets) {
    // Welcome to 2021!
}

Update your jQuery regularly

Putting a band-aid on a wound won't last long. Keeping your libraries updated is vital for the health of your code. Post updating, remember to test extensively to find any undiscovered issues.

Persistent issues

If errors persist even after updates, reach out to the coding community or contemplate a code overhaul complying with modern standards. Endorse feature detection over browser detection for sustainable results.

Strategies for preserving code integrity

Correct use of jQuery Migrate

Apply jQuery Migrate correctly, plugging it in after including the jQuery library. An incorrect use-case could lead you down a rabbit hole of issues:

<script src="https://code.jquery.com/jquery-3.x-git.min.js"></script>
<script src="https://code.jquery.com/jquery-migrate-3.x-git.min.js"></script>

Bullet-proof your code

Add safety checks to ensure that your code doesn't crumble if a future update deprecates something:

if (jQuery.browser && jQuery.browser.msie) {
  console.log("IE detected, enable 'Ancient Mode'?"); // Chuckles, anyone?
}

Stay ahead of updates

Keep tabs on deprecations in new jQuery versions. It's better to correct the impending issue today rather than scrambling for fixes later. The jQuery Core 1.9 Upgrade Guide should be your best friend in this endeavor.