[BUG] Snippet initialization with IE8 fails with minified code (works with un-minified code)

[MSNev]

There is an issue with the snippet version check ApplicationInsightsContainer when using === and !== matching the version with "2.0".

This check works with unminified version of SDK works without any issues in IE8/9 mode, but causes the SDK to fail to initialize properly when the minified version is used.

This is because of a difference in the way the minified code performs the 2 numeric comparisons for the snippet version for (version !== 2.0 and version === 2.0) which causes this to fail for IE8/9 and all other browsers.

This is because the snippet initializes the version as 2 (not 2.0 -- subtle issue) and IE8/9 treat this differently (integer vs float) for the way these are checked in the minified code, which results in this check failing only for the minified code -- it works for the un-minified code.

The correct fix for this (because we can't update all of the deployed snippet versions) is to change these 2 comparisons to use != and == instead of !== and ===.

As a workaround for anyone hitting this issue and assuming you CAN update the snippet used is to set the snippet version to 2.0 instead of 2.
So changing this minified code ,sv:"5",version:2,config:d to ,sv:"5",version:2.0,config:d

[MSNev]

This is quite a bit more complicated than originally determined.
For the current version on the CDN, the only really work-around it to use the 2.5 version from the CDN as it's not the version number from the snippet as originally diagnosed.

The underlying root cause is a combination of items, simplistically, it is not a bug in any 1 component but the way all 3 are interacting.

This issue only affects the pre-minified bundle which is included in the NPM packages and deployed to the CDN, the main un-minified code works with IE8 and depending on the minifier you use and the level of minification performed will determine whether the issue reproduces.

What is the issue?

• As part of minification for Application Insights we use @microsoft/dynamicProto to remove the un-minifier Class.prototype.xxxx in the generated code.
• This works fine for un-minified code
• For minification we use Uglify-JS v3 and as part of the "minification" process when a "class" doesn't have any static or class level functions (which is what happens when we use "dynamicProto") the "class" effectively becomes an object that is "linked" to the class function during creation.
• All of the above works perfectly on all browsers (minified or un-minified) "except" for IE8, where the minification step of creating an object class does not "keep" the link with the "constructor" (class) function, so when dynamicProto successfully creates the prototype functions the object is not linked with the prototype, so the class functions don't exist..

If however, the class has a non-dynamic prototype or static function the minification process doesn't cause this issue....

Investigating possible solutions.

[github-actions]

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