one-off.js

(function(){
  // problem 1
  const curryJoin = a => b =>`${a}-${b}`;

  // test 1 (expected: 'foo-bar')
  console.log(curryJoin('foo')('bar'));

  
  // problem 2 (not the cleanest solution, but not bad for hand-written with a 5 minute time constraint)
  function pickGroup(groupsCollection){
    const resultArray = groupsCollection.reduce((arr, obj)=>{
      arr.push(...Array(obj.weight).fill(obj.group));
      return arr;
    }, []);
    return resultArray[Math.floor(Math.random() * resultArray.length)];
  }

  // test 2 (expected: red ~50% blue ~25% green ~25%)
  const groups = [{group:'red',weight:2}, {group:'blue',weight:1}, {group:'green',weight:1}];
  const iterations = 100000;
  const colors={red:0,green:0,blue:0};
  let i=0;
  let color;
  while(++i<iterations){ colors[pickGroup(groups)] += 1; }
  for(color in colors){ console.log(color, colors[color]/iterations); }
}());