为什么我的递归函数返回未定义？

Question

I don't understand why return weights_data returns undefined , and console.log(weights_data) returns something.

const getWeightReattributeProportionally = (weights_data, weight, z = 0) => {

  weights_data.forEach( (r, i) => weights_data[i] = (r * weight) + r );

  if ( weights_data.reduce( (a, b) => a + b) >= 0.9999999999999999 ) {

    console.log(weights_data);

    return weights_data;

  } else {

    getWeightReattributeProportionally(weights_data, weight *= weight, z += 1);

  }

}

const data = [0.12, 0.22, 0.32, 0.18]

const aaaa = getWeightReattributeProportionally(data, 0.16)

console.log(aaaa)

Answer 1

You forgot that you need to return the result of the recursive function:

 const func = (weights_data, weight, z = 0) => { weights_data.forEach((r, i) => weights_data[i] = (r * weight) + r) if (weights_data.reduce((a, b) => a + b) >= 0.9999999999999999) { console.log(weights_data) return weights_data } else { return func(weights_data, weight *= weight, z += 1) // NEW! } } const data = [0.12, 0.22, 0.32, 0.18] const aaaa = func(data, 0.16) console.log(aaaa)

Also, you have a bug in your code: z is never used anywhere in your function

Answer 2

Unless your recursive function uses side effects (eg, manipulating global/shared state, writing to a file, etc.) to do its job, every invocation, including the outermost, must return its results to its caller.

If it doesn't, how can the caller know what the recursive call did?