upgrade ts model dir

Author: peze

lib/builtin.js

@@ -136,10 +136,22 @@ class Number extends Builtin {
 
 class JSON extends Builtin {
   constructor(generator){
-    const methods = ['stringify'];
+    const methods = [];
     super(generator, 'JSON', methods);
   }
 
+  stringify(args) {
+    const expr = args[0];
+    this.generator.emit('typeof ');
+    this.generator.visitExpr(expr);
+    this.generator.emit(' === "string" ? ');
+    this.generator.visitExpr(expr);
+    this.generator.emit(' : ');
+    this.generator.emit('JSON.stringify(');
+    this.generator.visitExpr(expr);
+    this.generator.emit(')');
+  }
+
   parseJSON(args, level){
     this.generator.emit(`${this.module }.parse`);
     this.generator.visitArgs(args, level);