JS: Implement DI

inject.js

/**
 * Constructor DependencyInjector
 * @param {Object} - object with dependencies
 */
var DI = function (dependency) {
  this.dependency = dependency;
};

// Should return new function with resolved dependencies
DI.prototype.inject = function (func) {
  const deps = func
    .toString()
    .match(/^function \((.*)\)/)[1]
    .split(',')
    .map((it) => 
      this.dependency[it.trim()]
    )
    .filter((it) => it !== undefined);

  if(deps.length === 0) {
    return func;
  }

  return () => func(...deps);
}


var deps = {
  'dep1': function () {return 'this is dep1';},
  'dep2': function () {return 'this is dep2';},
  'dep3': function () {return 'this is dep3';},
  'dep4': function () {return 'this is dep4';}
};
  
var di = new DI(deps);

var myFunc = di.inject(function (dep3, dep1, dep2) {
  return [dep1(), dep2(), dep3()].join(' -> ');
});

Test.assertEquals(myFunc(), 'this is dep1 -> this is dep2 -> this is dep3');