refactor setTypeOf to more atomic helper methods

- reduces sideeffects as parser is called outside of helper
- allows better reuse

lib/ParserHelpers.js

@@ -25,16 +25,19 @@ ParserHelpers.addParsedVariableToModule = function(parser, name, expression) {
 	return true;
 };
 
-ParserHelpers.setTypeof = function setTypeof(parser, expr, value) {
-	parser.plugin("evaluate typeof " + expr, function(expr) {
-		return new BasicEvaluatedExpression().setString(value).setRange(expr.range);
-	});
-	parser.plugin("typeof " + expr, function(expr) {
+ParserHelpers.toConstantDependency = function toConstantDependency(value) {
+	return function(expr) {
 		var dep = new ConstDependency(JSON.stringify(value), expr.range);
 		dep.loc = expr.loc;
 		this.state.current.addDependency(dep);
 		return true;
-	});
+	};
+};
+
+ParserHelpers.evaluateToString = function setTypeof(value) {
+	return function(expr) {
+		return new BasicEvaluatedExpression().setString(value).setRange(expr.range);
+	};
 };
 
 ParserHelpers.expressionIsUnsupported = function expressionIsUnsupported(message) {