Question 251338 in Javascript Question posted in
A very good W3school tutorial can be found here.

Convert list to array in JavaScript

const list = {"value":10,"rest":{"value":20,"rest":null}};

function list_to_array(list) {
  arr = [];
  for (const property in list) {
    if (property == "value") {
      arr.push(property);
    } else if (property == "rest") {
      for (const property in rest) {
        arr.push(property);
      }
    }
  }
}
console.log(JSON.stringify(list_to_array(x)));

but I get the error Uncaught ReferenceError ReferenceError: rest is not defined how can I iterate in the rest object ? or how would you do this function

this functions transform a list to an array

Tags:

2

Answers


  1. 0

    This line x = array_to_list([10, 20]); could be x = list_to_array([10, 20]);

    Login or Signup to reply.
  2. 0

    You need to use a recursion here, if you the property is "rest". In addition to get the value use list[property]:

    function list_to_array(list) {
  const arr = [];
  
  for (const property in list) {
    if (property == "value") {
      arr.push(list[property]);
    } else if (property == "rest") {
      arr.push(...list_to_array(list[property])); // call list_to_array on the rest
    }
  }
  
  return arr; // return the arr
}

const list = {"value":10,"rest":{"value":20,"rest":null}};

const result = list_to_array(list);

console.log(JSON.stringify(result));

    However, you can shorten this recursion easily:

    function list_to_array({ value, rest } = {}, arr = []) {
  arr.push(value);
  return rest ? list_to_array(rest, arr) : arr;
}

const list = {"value":10,"rest":{"value":20,"rest":null}};

const result = list_to_array(list);

console.log(JSON.stringify(result));

    A simpler solution would be to use a while loop, and take the rest property value on each iteration:

    function list_to_array(list) {
  const arr = [];
  let current = list;
  
  do {
    arr.push(current?.value);
  } while(current = current?.rest);
  
  return arr; // return the arr
}

const list = {"value":10,"rest":{"value":20,"rest":null}};

const result = list_to_array(list);

console.log(JSON.stringify(result));
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search