Hello. This PR is a fix to #193523, which was labelled with both help-wanted and bug labels.

Useful summary of the issue:

• First, go to settings.json and add these 2 config lines:

"editor.suggest.preview": true,
"javascript.suggest.completeFunctionCalls": true,

• Then, in a JS file type the following:

/**
 * @param {string} one hi.
 * @param {number} two howdy.
 * @param {string} [three] hello.
 */
function test(one, two, three) { }

• Now, when you try to invoke the function test, you should notice that in the autocompletion preview the optional params have been omitted:

  

After applying the fix (based on @RyanCavanaugh advice), the problem is solved.