问lodash "set“方法的javascript实现

EN

const set = (obj, path, value) => {
    if (Object(obj) !== obj) return obj; // When obj is not an object
    // If not yet an array, get the keys from the string-path
    if (!Array.isArray(path)) path = path.toString().match(/[^.[\]]+/g) || []; 
    path.slice(0,-1).reduce((a, c, i) => // Iterate all of them except the last one
         Object(a[c]) === a[c] // Does the key exist and is its value an object?
             // Yes: then follow that path
             ? a[c] 
             // No: create the key. Is the next key a potential array-index?
             : a[c] = Math.abs(path[i+1])>>0 === +path[i+1] 
                   ? [] // Yes: assign a new array object
                   : {}, // No: assign a new plain object
         obj)[path[path.length-1]] = value; // Finally assign the value to the last key
    return obj; // Return the top-level object to allow chaining
};

// Demo
var obj = { test: true };
set(obj, "test.1.it", "hello");
console.log(obj); // includes an intentional undefined value

/**
 * @example
 * const obj = {id:1, address: {city: 'Minsk', street: 'Prityckogo 12'}}
 * setByString(obj, 'address.city', 'Grodno'); obj.address.city => 'Grodno'
 * setByString(obj, ['address', 'city'], 'Grodno'); obj.address.city => 'Grodno'
 * setByString(obj, ['address', city', 'phones'], {mobile: 1234, home: 222}); obj.address.city.phones.home => 222
*/

/**
* @param    {any}   input
* @return   {boolean}
*/

const isObject = (input) => (
  null !== input && 
    typeof input === 'object' &&
    Object.getPrototypeOf(input).isPrototypeOf(Object);
)

 **/
 * @param   {object}    obj
 * @param   {string}    path
 * @param   {any}       value
 */

const setByString = (obj, path, value) => {
  const pList = Array.isArray(path) ? path : path.split('.');
  const len = pList.length;
  // changes second last key to {}
  for (let i = 0; i < len - 1; i++) {
    const elem = pList[i];
    if (!obj[elem] || !isObject(obj[elem])) {
      obj[elem] = {};
    }
    obj = obj[elem];
  }

  // set value to second last key
  obj[pList[len - 1]] = value;
};

const set = (obj = {}, paths = [], value) => {
    const inputObj = obj === null ? {} : { ...obj };

    if (paths.length === 0) {
        return inputObj;
    }

    if (paths.length === 1) {
        const path = paths[0];
        inputObj[path] = value;
        return { ...inputObj, [path]: value };
    }

    const [path, ...rest] = paths;
    const currentNode = inputObj[path];

    const childNode = set(currentNode, rest, value);

    return { ...inputObj, [path]: childNode };
};