A simple typescript script that parses json paths and composes a lense function

jsonpath.ts

function extractorFor(selector: String): (x: any) => any {

  function composeAccess(f: (x: any) => any, field: string): (x: any) => any {
    return (x: any) => {
      let r = f(x)
      if (field in r) return r[field]
      else return null
    }
  }

  function identity(x: any): any {
    return x
  }
  
  function nonEmpty(x: string): boolean {
  	return x != ""
  }
  
  function unescape(x: string): string {
  	return x.replace('~1', '/').replace('~0', '~')
  }
  
  return selector.split('/')
                 .filter(nonEmpty)
                 .map(unescape)
                 .reduce(composeAccess, identity)
}

function extract(o: any, selector: string): any {
	return extractorFor(selector)(o)
}

let selector = "/passengers/0/flights/0/segments/0/services/seat/number~1a"
let compiled = extractorFor(selector)

let obj = {
	passengers: [{
    flights: [{
      segments: [{
        services: {
          seat: {
            "number/a": '1A'
          }
        }
      }]
    }]
  }]
}

console.log("object", JSON.stringify(obj))
console.log("selector", selector)
console.log("result", compiled(obj))