@mzvonar/setin/dist/index.js

Sets value to object according to provided path and returns copy

"use strict";

/**
 * Sets value in object according to provided path
 * @param {Object} context
 * @param {Array|string} path
 * @param {*} value
 * @param {Boolean} push If set to true and last object in path is Array value is pushed to the array
 * @return {Object} Copy of object with new value set
 */
function createSetIn(mutable) {
  return function setIn(context, path, value, push) {
    if (typeof path === 'undefined' || path === null) {
      throw new Error('Path is undefined');
    }

    var pathType = Object.prototype.toString.call(path);

    if (pathType !== '[object Undefined]' && pathType !== '[object Array]') {
      path = [path];
    } else {
      path = [].concat(path);
    }

    var currentPathPart = path.shift();

    if (typeof currentPathPart === 'undefined' || currentPathPart === null) {
      throw new Error('Path part is undefined');
    }

    if (!context) {
      context = {};
    }

    var currentValue = path.length === 0 ? value : setIn(context[currentPathPart], path, value, push);
    var contextType = Object.prototype.toString.call(context);

    if (contextType === '[object Array]') {
      var copy = mutable ? context : [].concat(context);
      copy[currentPathPart] = currentValue;
      return copy;
    } else if (contextType === '[object Object]') {
      var copy = mutable ? context : {};

      if (push && path.length === 0) {
        contextType = Object.prototype.toString.call(context[currentPathPart]);

        if (contextType !== '[object Array]' && contextType !== '[object Undefined]') {
          throw new Error('Cannot push to ' + contextType);
        }

        if (contextType === '[object Undefined]') {
          copy[currentPathPart] = [];
        } else {
          copy[currentPathPart] = mutable ? context[currentPathPart] : [].concat(context[currentPathPart]);
        }

        copy[currentPathPart].push(value);
      } else {
        copy[currentPathPart] = currentValue;
      }

      return mutable ? context : Object.assign({}, context, copy);
    } else {
      throw new Error('Trying to add property to ' + contextType);
    }
  };
}

module.exports = createSetIn();
module.exports.mutableSetIn = createSetIn(true);