Recursive searching returns undefined-CodePudding

I was just practicing some native Javascript and came across this problem. I'm building a comments widget and trying to implement a 'reply' button. For this I have to iterate through some n number of nested comments to find the correct one and push the reply to it's 'responses' attribute. This is my code so far:

 const recursiveSearch = (object, target) => {
    if(object.id === target) return object;

    let result;
    if(object.responses.length > 0) {
     object.responses.forEach(response => {
          if(response.id === target) {
              result = response;
              console.log('match found')
              console.log(response)
              return response
          } 
          
          else if(response.responses.length > 0) recursiveSearch(response, target) 
      })   
    };

    console.log('result Is')
    console.log(result)

    return result

}

The logs show the expected behavior just fine but when looking at the end return statement is undefined. Any way to get around this?

CodePudding user response：

You should return from the recursive call and assign to the result variable again.

const recursiveSearch = (object, target) => {
  if (object.id === target) return object;

  let result;
  if (object.responses.length > 0) {
    object.responses.forEach(response => {
      if (response.id === target) {
        result = response;
        console.log('match found')
        console.log(response)
        return response
      }

      else if (response.responses.length > 0) {
        result = recursiveSearch(response, target) // <--------------------
      }
    })
  };

  console.log('result Is')
  console.log(result)

  return result
}

You can also use a find instead of forEach. This is more efficient.

const recursiveSearch = (object, target) => {
  if (object.id === target) return object;

  const result = object.responses.find(response => {
    if (response.id === target) {
      console.log('match found')
      console.log(response)
      return response
    }

    else if (response.responses.length > 0) {
      return recursiveSearch(response, target)
    }
  })

  console.log('result Is')
  console.log(result)

  return result
}

CodePudding user response：

You forgot to return in your else if, but notice, you're inside a forEach, so maybe change it to regular for or use something else