Strip URL parameters (GTM Custom JS Variable). Useful for preventing PII from being tracked.

gtm-variable-ga-page-custom.js

/**
 * Returns the current page URL with the specified paramaters stripped.
 * Only includes the path + querystring, as this is intended for overriding `page` field of GA Pageview.
 * @version 0.1.0
 */
function() {
  // The params to strip. Case-insensitive. Escape (with a double-backslash) 
  //   any regex special chars (unless using regex intentionally).
  var params = [ 'name', 'email' ];
  // You could define the paramaters list as a comma-limited list like this
  //  instead (but ensure there's no space around commas).
  //var params = 'name,email,phone,address'.split(',');
  
  // No paramaters to replace.
  if( ! location.search ) return;

  return location.pathname + (function(){
    var i, search = location.search;
    // Remove each specified parameter, regardless of format (p or p= or p=value) or position in the querystring.
    for( i=0; i<params.length; i++ ){
      search = search.replace( new RegExp( '([?&])'+params[i]+'(=[^&]*)?&?', 'gi' ), '$1' ); }
    // Trim trailing "&"s, and remove "?" if all params removed.
    return search.replace( /&+$/, '' ).replace( /^\?$/, '' );
  })();
}

Could improve perf by moving regex out of loop using method shown in this solution - https://stackoverflow.com/a/37949642/445295