:sparkles: remove require loop
add underscore.js to global variables in test
:bug: fix to require needed module
:sparkles: fix definition of parseEnvironmentExpression
:fire: remove unused code
:sparkles: fix to remove parser.state disallowGenerator
:sparkles: fix to remove parser.state closedFunction
:fire: fix to remove unused parser.state binaryPrecedence
:sparkles: fix code layout
:sparkles: fix to refine parseIdentifier
:sparkles: fix to refine parseLiteral
:sparkles: fix to refine parseEnvironmentExpression
:sparkles: fix to refine parseThisExpression
:sparkles: fix to refine parseRefExpression
:sparkles: fix to refine parseSignedExpression
:sparkles: fix to refine parseSeriesExpression
:sparkles: fix to refine parseProgram
:sparkles: fix to refine parseEventExpression
:sparkles: change method name
:sparkles: fix to refine parseLabelAsSymbol