フォルダ階層たどってJSONにしてくれるの

files.js

module.exports = `
foo.html
bar/hoge/fuga.php
bar/hoge/piyo.php
bar/hogera.php
baz/fugara.php
`

index.js

const files = require("./files")
const res = files
    .split("\n")
    .filter(v => v !== "")
    .map(path => path.split("/"))
    .reduce((acc, filepath) => {
        const last = filepath.pop()
        const fn = (acc, arr, last) => {
            if (arr.length === 0) {
                acc.push(last)
                return
            }
    
            const key = arr.shift()
            const find = acc.find(obj =>
                    typeof obj === "object"
                    && key in obj)
            const crrent = { [key]: [] }
            if (!find) {
                acc.push(crrent)
            }
            fn(find ? find[key] : crrent[key], arr, last)
        }
        fn(acc, filepath, last)
        return acc
    }, [])

console.log(JSON.stringify(res, null, ' '))
// [
//     "foo.html",    
//     {
//      "bar": [      
//       {
//        "hoge": [   
//         "fuga.php",
//         "piyo.php" 
//        ]
//       },
//       "hogera.php" 
//      ]
//     },
//     {
//      "baz": [      
//       "fugara.php" 
//      ]
//     }
// ]