If the function isn't used in the code in any way, it will get stripped from the production output due to a process called tree shaking. It's an optimization that looks at code imports and then eliminates any unused code as a result.
It turns out that was the case here as each wasn't used and it was imported only.
» npm install lodash-es
Correct way to import lodash
Merge lodash-es into lodash package
ts node - How to use lodash-es in typescript correctly? - Stack Overflow
lodash-es modules should be published to NPM with ".mjs" extension
import has from 'lodash/has'; is better because lodash holds all its functions in a single file, so rather than import the whole 'lodash' library at 100k, it's better to just import lodash's has function which is maybe 2k.
If you are using webpack 4, the following code is tree shakable.
import { has } from 'lodash-es';
The points to note;
CommonJS modules are not tree shakable so you should definitely use
lodash-es, which is the Lodash library exported as ES Modules, rather thanlodash(CommonJS).lodash-es's package.json contains"sideEffects": false, which notifies webpack 4 that all the files inside the package are side effect free (see https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free).This information is crucial for tree shaking since module bundlers do not tree shake files which possibly contain side effects even if their exported members are not used in anywhere.
Edit
As of version 1.9.0, Parcel also supports "sideEffects": false, threrefore import { has } from 'lodash-es'; is also tree shakable with Parcel.
It also supports tree shaking CommonJS modules, though it is likely tree shaking of ES Modules is more efficient than CommonJS according to my experiment.
You can load types from here:
npm install --save-dev @types/lodash-es
And use it like:
import { camelCase } from "lodash-es"
ts-node compiles .ts files as they are loaded. It doesn't touch .js files; either they must already be in a form understood by Node.js (e.g., no ES6 import statements) or you must use a separate mechanism to transform them, such as the @babel/register require hook (essentially the same thing that is used by babel-node). You would still need to configure @babel/register not to ignore node_modules, as described in the other answer. The advice from the other answer to just use lodash instead of lodash-es is good.
» npm install @types/lodash-es