Case-insensitive get like lodash's _.get()

geti

function geti (value, prop) {
  if (_.isPlainObject(value)) {
    if (_.isString(prop) && prop !== '') {
      return geti(value, prop.split('.'));
    } else if (_.isArray(prop) && prop.length) {
      const key = _.toLower(prop.shift()),
          val = Object.keys(value).reduce(function (a, k) {
            if (a !== undefined) {
              return a;
            }
            if (_.toLower(k) === key) {
              return value[k];
            }
          }, undefined);
      if (prop.length) {
        let v = geti(val, prop);
        return v === undefined ? defaultValue : v;        
      }
      return val === undefined ? defaultValue : val;
    }
  }
  throw new Error(`iget value argument must be an object`);
}

This one does not work with array accessor... e.g. data[0]
Test before using...

Since the above solution is using lodash, here's a working implementation:

const _ = require('lodash');
const castPath = require('lodash/_castPath');
const toKey = require('lodash/_toKey');

function geti(object, path, defaultValue) {
  if (!object) return defaultValue === undefined ? null : defaultValue;

  const paths = castPath(path, object);
  const { length } = paths;
  let index = 0;

  let iterator = object;
  while (iterator != null && index < length) {
    const key = (toKey(paths[index])).toLowerCase();
    iterator = findLowercaseKey(iterator, key);
    index += 1;
  }
  return (index && index === length) ? iterator : defaultValue;
}

function findLowercaseKey(value, key) {
  return Object.keys(value).reduce((a, k) => {
    if (a !== undefined) {
      return a;
    }
    if (_.toLower(k) === key) {
      return value[k];
    }
  }, undefined);
}

module.exports = {
  geti,
};

The code above is working (and helped me). But it needs a little change so it returns the right defaultValue:

return (index && index === length && iterator)
  ? iterator
  : defaultValue;

The above code is amazing, but it would fail in the case of geti( {did: 0,}, "did" ) because 0 == null.
Here is a working version:

const toLower = require( "lodash/toLower" );
const castPath = require( "lodash/_castPath" );
const toKey = require( "lodash/_toKey" );

module.exports = ( object, path, defaultValue ) => {
	if( !object ) return defaultValue === undefined ? null : defaultValue;

	const paths = castPath( path, object );
	const { length } = paths;
	let index = 0;

	let iterator = object;
	while( iterator !== undefined && index < length ){
		const key = (toKey( paths[index] )).toLowerCase();
		iterator = findLowercaseKey( iterator, key );
		index += 1;
	}
	return (index && index === length && iterator !== undefined) ? iterator : defaultValue;
}

const findLowercaseKey = ( value, key ) => {
	return Object.keys( value ).reduce( ( a, k ) => {
		if( a !== undefined ){
			return a;
		}
		if( toLower( k ) === key ){
			return value[k];
		}
	}, undefined );
}