所有的节点的transform方法都对应同一个函数:

node.DEFMETHOD("transform", function(tw, in_list){            var x, y;            tw.push(this);            if (tw.before) x = tw.before(this, descend, in_list);            if (x === undefined) {                if (!tw.after) {                    x = this;                    descend(x, tw);                } else {                    tw.stack[tw.stack.length - 1] = x = this.clone();                    descend(x, tw);                    y = tw.after(x, in_list);                    if (y !== undefined) x = y;                }            }            tw.pop();            return x;        });

不同的是每个节点可以有不同的descend方法 

AST_Node的descend方法为一个空函数

以下节点有自定义的descend方法

AST_LabeledStatement,AST_SimpleStatement,AST_Block,AST_DWLoop,AST_For,AST_ForIn,

AST_With,AST_Exit,AST_LoopControl,AST_If,AST_Switch,AST_Case,AST_Try,AST_Catch,

AST_Definitions,AST_VarDef,AST_Lambda,AST_Call,AST_Seq,AST_Dot,AST_Sub,

AST_Unary,AST_Binary,AST_Conditional,AST_Array,AST_Object,AST_ObjectProperty