I hope this question/answer saves time for those having the same cross-compatibility issues with internet explorer.
Problem: I used vuejs2 in one of my projects, and it turned out that there were some compatibility issues in earlier releases of internet explorer.
at first, it went down to this error:
SCRIPT1014: Invalid character
And then this one:
'Promise' is undefined
the first error refers to the use of Ecmascript6 back thicks (`) that simplifies the use of strings in javascript. the solution is to use the old way which is concatenating your HTML.
As for the second error, the use of promises is not handled in earlier versions of internet explorer, the solution is to use polyfill (which is an api that ensures backwards compatibility in older browsers, example: promises)
in my case I used this:
<script src='https://cdn.polyfill.io/v2/polyfill.min.js'></script>