Find `const` usage in javascript file

parse.js

const fs = require('fs')
const rocambole = require('rocambole');

// Use espree instead of esprima - about twice as fast
const espree = require('espree');
rocambole.parseFn = espree.parse;
rocambole.parseContext = espree;

const parseTime = (delta) => (delta[0] * 1000 + delta[1] / 1e6) + 'ms'

const args = process.argv.slice(2)
const fileName = args[0]

if (!fileName) {
  throw new Error("File path expected as first argument");
}
fs.statSync(fileName) // Throws if file doesn't exist


const start = process.hrtime()
const data = fs.readFileSync(fileName).toString()
console.log('Loaded:', fileName, 'in:', parseTime(process.hrtime(start)))

var constUsages = [];

const startAst = process.hrtime()
const ast = rocambole.parse(data, { ecmaVersion: 6 })
console.log('Parsed AST in:', parseTime(process.hrtime(startAst)));

console.log('Beginning moonwalk.')
const startWalk = process.hrtime()
rocambole.moonwalk(ast,(node) => {
  if (node.type == 'VariableDeclaration'){
    if (node.kind === 'const') {
      constUsages.push(node)
    }
  }
});
console.log('Treewalk finished in:', parseTime(process.hrtime(startWalk)));

console.log('Const Usage:', constUsages)
console.log('Const count:', constUsages.length)