convert a JSON keys to camel case

convertToCamelCase.js

// convert a key string to camelcase
function toCamelCase(str) {
  // when str is not define reuturn
  if (!str) {
    return str;
  }

  let letters = str.split("");
  let idx = letters.indexOf("_");
  while (idx > -1) {
    // if '_'  is not first or last character
    // then capitalize next character
    if (idx !== 0 && letters.length > idx + 1) {
      const nextLetter = letters[idx + 1];
      letters[idx + 1] = nextLetter.toUpperCase();
    }
    // remove '_' character
    letters.splice(idx, 1);
    // get the index of next '_' character
    idx = letters.indexOf("_");
  }
  // return str in camel case
  return letters.join("");
}

// convert all keys in a json to camelcase
// NOTE: JSON parsing is not done here
// so before calling this function JSON should be parsed
function convertToCamelCase(json) {
  // check if it is an array
  if (Array.isArray(json)) {
    return json.map(el => convertToCamelCase(el));
  }

  // check if it is an object
  if (typeof json === "object") {
    let newJson = { ...json };
    Object.keys(newJson).forEach(key => {
      // convert the key to camel case
      const newKey = toCamelCase(key);
      // copy the converted value of this key to a new variable
      const value = convertToCamelCase(newJson[key]);
      // remove the key from the json
      delete newJson[key];
      // replace the value under new converted key
      newJson[newKey] = value;
    });
    return newJson;
  }

  // if it is not object or array
  // then return as it is
  return json;
}