Set termType directly on class.

Fixes #172

lib/N3DataFactory.js

@@ -14,11 +14,6 @@ class Term {
     this.id = id;
   }
 
-  // ### The term type of this term
-  get termType() {
-    return this.constructor.name;
-  }
-
   // ### The value of this term
   get value() {
     return this.id;
@@ -46,12 +41,20 @@ class Term {
 
 
 // ## NamedNode constructor
-class NamedNode extends Term {}
-NamedNode.name = 'NamedNode';
-
+class NamedNode extends Term {
+  // ### The term type of this term
+  get termType() {
+    return 'NamedNode';
+  }
+}
 
 // ## Literal constructor
 class Literal extends Term {
+  // ### The term type of this term
+  get termType() {
+    return 'Literal';
+  }
+
   // ### The text value of this literal
   get value() {
     return this.id.substring(1, this.id.lastIndexOf('"'));
@@ -103,32 +106,39 @@ class Literal extends Term {
     };
   }
 }
-Literal.name = 'Literal';
 
 // ## BlankNode constructor
 class BlankNode extends Term {
   constructor(name) {
     super('_:' + name);
   }
 
+  // ### The term type of this term
+  get termType() {
+    return 'BlankNode';
+  }
+
   // ### The name of this blank node
   get value() {
     return this.id.substr(2);
   }
 }
-BlankNode.name = 'BlankNode';
 
 class Variable extends Term {
   constructor(name) {
     super('?' + name);
   }
 
+  // ### The term type of this term
+  get termType() {
+    return 'Variable';
+  }
+
   // ### The name of this variable
   get value() {
     return this.id.substr(1);
   }
 }
-Variable.name = 'Variable';
 
 // ## DefaultGraph constructor
 class DefaultGraph extends Term {
@@ -137,6 +147,11 @@ class DefaultGraph extends Term {
     return DEFAULTGRAPH || this;
   }
 
+  // ### The term type of this term
+  get termType() {
+    return 'DefaultGraph';
+  }
+
   // ### Returns whether this object represents the same term as the other
   equals(other) {
     // If both terms were created by this library,
@@ -145,7 +160,6 @@ class DefaultGraph extends Term {
     return (this === other) || (!!other && (this.termType === other.termType));
   }
 }
-DefaultGraph.name = 'DefaultGraph';
 
 // ## DefaultGraph singleton
 DEFAULTGRAPH = new DefaultGraph();