A rough implemention of augularjs $inject.

inject.js

var DI = function (dependency) {
  this.dependency = dependency;
};

function readParams(func) {
  const fs = func.toString()
  const paramsMatch = fs.match(/^function.*\((.*?)\)/) || fs.match(/(.*?)\s*\=\>/)
  if (!paramsMatch) throw ''

  const paramsStr = paramsMatch[1].replace(/[\(\)]/g, '')
  const params = paramsStr.split(',').map(param => param.trim()).filter(_ => _)

  return params
}

DI.prototype.inject = function (func) {
  const paramsPattern = readParams(func)
  const params = paramsPattern.map(paramName => this.dependency[paramName])
  
  return () => func(...params)
}


// tests
const di = new DI({
  'dep1': () => 'dep1',
  'dep2': () => 'dep2',
  'dep3': () => 'dep3',
  'dep4': () => 'dep4'
})

const f = di.inject(function (dep3, dep1, dep2) {
  return [dep1(), dep2(), dep3()].join(' -> ')
})
console.log(f() === 'dep1 -> dep2 -> dep3') // true
console.log(di.inject((dep2, dep3) => dep2() + dep3())() === 'dep2dep3') // true