LibJS: Implement While statements

Libraries/LibJS/AST.cpp

@@ -71,6 +71,16 @@ Value IfStatement::execute(Interpreter& interpreter) const
         return interpreter.run(*m_alternate);
 }
 
+Value WhileStatement::execute(Interpreter& interpreter) const
+{
+    Value last_value = js_undefined();
+    while (m_predicate->execute(interpreter).as_bool()) {
+        last_value = interpreter.run(*m_body);
+    }
+
+    return last_value;
+}
+
 Value add(Value lhs, Value rhs)
 {
     ASSERT(lhs.is_number());
@@ -259,4 +269,14 @@ void IfStatement::dump(int indent) const
     alternate().dump(indent + 1);
 }
 
+void WhileStatement::dump(int indent) const
+{
+    ASTNode::dump(indent);
+
+    print_indent(indent);
+    printf("While\n");
+    predicate().dump(indent + 1);
+    body().dump(indent + 1);
+}
+
 }

Libraries/LibJS/AST.h

@@ -151,6 +151,27 @@ private:
     NonnullOwnPtr<ScopeNode> m_alternate;
 };
 
+class WhileStatement : public ASTNode {
+public:
+    WhileStatement(NonnullOwnPtr<Expression> predicate, NonnullOwnPtr<ScopeNode> body)
+        : m_predicate(move(predicate))
+        , m_body(move(body))
+    {
+    }
+
+    const Expression& predicate() const { return *m_predicate; }
+    const ScopeNode& body() const { return *m_body; }
+
+    virtual Value execute(Interpreter&) const override;
+    virtual void dump(int indent) const override;
+
+private:
+    virtual const char* class_name() const override { return "WhileStatement"; }
+
+    NonnullOwnPtr<Expression> m_predicate;
+    NonnullOwnPtr<ScopeNode> m_body;
+};
+
 enum class BinaryOp {
     Plus,
     Minus,