allow variable intializer substitution

transpiler/src/main/java/org/jsweet/transpiler/Java2TypeScriptTranslator.java

@@ -2693,11 +2693,11 @@ public class Java2TypeScriptTranslator extends AbstractTreePrinter {
 		} else if (var.init == null) {
 			if (doesMemberNameRequireQuotes(name)) {
 				printIndent().print("if(").print("this['").print(name).print("']").print("===undefined) ")
-						.print("this['").print(name).print("'] = ").print(Util.getTypeInitialValue(var.type)).print(";")
+						.print("this['").print(name).print("'] = ").print(getAdapter().getVariableInitialValue(var.sym)).print(";")
 						.println();
 			} else {
 				printIndent().print("if(").print("this.").print(name).print("===undefined) this.").print(name)
-						.print(" = ").print(Util.getTypeInitialValue(var.type)).print(";").println();
+						.print(" = ").print(getAdapter().getVariableInitialValue(var.sym)).print(";").println();
 			}
 		}
 	}
@@ -2863,7 +2863,7 @@ public class Java2TypeScriptTranslator extends AbstractTreePrinter {
 						name = context.getFieldNameMapping(field.sym);
 					}
 					printIndent().print("if(").print("this.").print(name).print("===undefined) ").print("this.")
-							.print(name).print(" = ").print(Util.getTypeInitialValue(field.type)).print(";").println();
+							.print(name).print(" = ").print(getAdapter().getVariableInitialValue(field.sym)).print(";").println();
 				}
 			}
 		}
@@ -3340,7 +3340,7 @@ public class Java2TypeScriptTranslator extends AbstractTreePrinter {
 				// var initialization is not allowed in definition
 				if (!isDefinitionScope && !(ambient || (isTopLevelScope() && isDefinitionScope))
 						&& varDecl.sym.isStatic() && varDecl.init == null) {
-					print(" = ").print(Util.getTypeInitialValue(varDecl.sym.type));
+					print(" = ").print(getAdapter().getVariableInitialValue(varDecl.sym));
 				}
 			}
 		}

transpiler/src/main/java/org/jsweet/transpiler/extension/PrinterAdapter.java

@@ -32,6 +32,7 @@ import javax.lang.model.element.Name;
 import javax.lang.model.element.PackageElement;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.TypeParameterElement;
+import javax.lang.model.element.VariableElement;
 import javax.lang.model.type.DeclaredType;
 import javax.lang.model.type.TypeMirror;
 import javax.lang.model.util.Types;
@@ -740,7 +741,19 @@ public class PrinterAdapter {
 	 */
 	public boolean substituteVariableAccess(VariableAccessElement variableAccess) {
 		return parentAdapter == null ? false : parentAdapter.substituteVariableAccess(variableAccess);
+	}
 
+	/**
+	 * Called if the initializer of a variable is undefined (in order to force a
+	 * default value).
+	 * 
+	 * @param variable
+	 *            the variable to return an initializer for
+	 * @return an initializer expression, null to keep undefined
+	 */
+	public String getVariableInitialValue(VariableElement variable) {
+		return parentAdapter == null ? util().getTypeInitialValue(variable.asType())
+				: parentAdapter.getVariableInitialValue(variable);
 	}
 
 	/**

transpiler/src/main/java/org/jsweet/transpiler/model/Util.java

@@ -106,4 +106,9 @@ public interface Util {
 	 */
 	String getRelativePath(String fromPath, String toPath);
 
+	/**
+	 * Returns the literal for a given type initial value.
+	 */
+	String getTypeInitialValue(TypeMirror type);
+
 }

transpiler/src/main/java/org/jsweet/transpiler/model/support/UtilSupport.java

@@ -23,6 +23,7 @@ import java.util.List;
 import javax.lang.model.element.Element;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.type.DeclaredType;
+import javax.lang.model.type.TypeKind;
 import javax.lang.model.type.TypeMirror;
 
 import org.jsweet.transpiler.JSweetContext;
@@ -180,5 +181,22 @@ public class UtilSupport implements Util {
 	public String getRelativePath(String fromPath, String toPath) {
 		return org.jsweet.transpiler.util.Util.getRelativePath(fromPath, toPath);
 	}
+	
+	@Override
+	public String getTypeInitialValue(TypeMirror type) {
+		if (type == null) {
+			return "null";
+		}
+		if (isNumber(type)) {
+			return "0";
+		} else if (type.getKind() == TypeKind.BOOLEAN) {
+			return "false";
+		} else if (type.getKind() == TypeKind.VOID) {
+			return null;
+		} else {
+			return "null";
+		}
+	}
+	
 
 }

transpiler/src/main/java/org/jsweet/transpiler/util/Util.java

@@ -1288,7 +1288,7 @@ public class Util {
 	/**
 	 * Returns the literal for a given type inital value.
 	 */
-	public static String getTypeInitialValue(Type type) {
+	public static String getTypeInitialValue(TypeMirror type) {
 		if (type == null) {
 			return "null";
 		}