recursive

Array.prototype.forEachRecursive = function (callback, startIndex = 0, index = startIndex) {
  if (index >= this.length) {
    return;
  }

  const shouldContinue = callback(this[index], index, this);
  if (!shouldContinue) {
    return; // Break the iteration
  }

  this.forEachRecursive(callback, startIndex, index + 1);
};

((claims, agents) => {
  const result = [];
  let startAgentIndex = 0;

  claims.forEachRecursive((claim, claimIndex) => {
    if (!claim) return true;

    let remainedClaim = claim;
    
    const paidBy = [];

    const cb = (agent, agentIndex, _agents) => {
      startAgentIndex = agentIndex
      if (agent.budget >= remainedClaim) {
        _agents[agentIndex].budget = _agents[agentIndex].budget - remainedClaim;
        paidBy.push(agent.name);
        result.push({ claimIndex, paidBy });
        return false; // break the loop
      } else if (agent.budget > 0) {
        remainedClaim -= agent.budget;
        _agents[agentIndex].budget = 0;
        paidBy.push(agent.name);
      }
      return true
    }
    
    agents.forEachRecursive(cb, startAgentIndex);
 
    return startAgentIndex < agents.length; // Break the iteration in case there is no more agents
  });

  console.log(JSON.stringify(result, null, 2));
})(
  [14, 10, 20],
  [
    { name: "a1", budget: 10 },
    { name: "a2", budget: 4 },
    { name: "a3", budget: 40 },
  ]
);