code: function parseEqualityExpression() {
          var expr = parseRelationalExpression();
  
          while (match('==') || match('!=') || match('===') || match('!==')) {
              expr = {
                  type: Syntax.BinaryExpression,
                  operator: lex().value,
                  left: expr,
                  right: parseRelationalExpression()
              };
          }
  
          return expr;
      }
docs: 11.9 Equality Operators