estraverse_traverse.js

var esprima = require("esprima");
var estraverse = require("estraverse");

var ast = esprima.parse(`
function level1() {
	function level2() {
    	;
    }
}
function level1_1() {
    ;
}
`);

estraverse.traverse(ast, {
  enter: enter,
  leave: leave
});

function enter(node) {
  if (node.type === "FunctionDeclaration") {
    console.log("enter function: ", node.id.name);
  }
}

function leave(node) {
  if (node.type === "FunctionDeclaration") {
    console.log("leave function: ", node.id.name);
  }
}