package.json

{
  "scripts": {
    "start": "react-app-rewired start",
    "build": "react-app-rewired build",
    "test": "react-app-rewired test --env=jsdom"
  },
  "devDependencies": {
    "@babel/plugin-proposal-optional-chaining": "^7.2.0",
    "customize-cra": "^0.4.1",
    "react-app-rewired": "^2.1.3"
  }
  ...other
}

config-overrides.js

const { useBabelRc, override } = require('customize-cra');
module.exports = override(useBabelRc());

.babelrc

{
  "plugins": ["@babel/plugin-proposal-optional-chaining"]
}

detailed blogpost

Maybe that you are trying to access a property of an object that may be null or undefined before the initialization. To avoid this error, you have a few options:

You can check if the object is null or undefined before trying to access its properties. For example:

if (Targetfarms) {
  console.log(Targetfarms.placeId);
}

You can set a default value for Targetfarms using the || operator. For example:

const {Targetfarms} = useSelector((state: RootState) => state.post) || {};
console.log(Targetfarms.placeId);

This will set the default value of Targetfarms to an empty object, which means you can access its properties without getting an error.

Note: I think and it's only my opinion here, optional chaining it's a good approach to avoid null or undefined.

Well, I didn't want to use Babel because then I'd have to figure out how to replace ts-node. There's a bunch of outdated docs out there referring to old Babel packages, but these instructions should work as of Nov 2019:

Add a .babelrc file:

Copy{
    "presets": [
        ["@babel/preset-env",{"targets": {"node": "current"}}],
        "@babel/preset-typescript"
    ],
    "plugins": [
        "@babel/plugin-syntax-bigint"
    ]
}

Add these deps:

Copy  "devDependencies": {
    "@babel/cli": "^7.7.0",
    "@babel/core": "^7.7.0",
    "@babel/node": "^7.7.0",
    "@babel/plugin-syntax-bigint": "^7.4.4",
    "@babel/preset-env": "^7.7.1",
    "@babel/preset-typescript": "^7.7.0",
    "@types/node": "^12.7.5",
    "typescript": "^3.7.2"
  }

Execute your code with:

Copynode_modules/.bin/babel-node --extensions ".ts" src/index.ts

The --extensions ".ts" is very important, even though you're explicitly trying to execute a .ts file, it won't transpile it w/out that.

I like to use GNU Make instead of package.json scripts:

CopyMAKEFLAGS += --no-builtin-rules
.SUFFIXES:
NM := node_modules/.bin
.PHONY: build start dev clean test publish

## commands
########################################

__default:
    $(error Please specify a target)

build: build-types build-js dist/package.json

build-types: node_modules/.yarn-integrity
    $(NM)/tsc --emitDeclarationOnly

build-js: node_modules/.yarn-integrity
    $(NM)/babel src --out-dir dist --extensions ".ts" --source-maps inline

run: node_modules/.yarn-integrity
    $(NM)/babel-node --extensions ".ts" src/index.ts

check: node_modules/.yarn-integrity
    $(NM)/tsc --noEmit

dist:
    mkdir -p $@

clean:
    rm -rf node_modules dist yarn-error.log

dist/package.json: package.json | dist
    jq 'del(.private, .devDependencies, .scripts, .eslintConfig, .babel)' $< > $@

## files
########################################

node_modules/.yarn-integrity: yarn.lock
    @yarn install --frozen-lockfile --production=false --check-files
    @touch -mr $@ $<

yarn.lock: package.json
    @yarn check --integrity
    @touch -mr $@ $<

Or just copy from Microsoft's TypeScript Babel Starter.

Update Oct 15, 2019

Support now exists in [email protected]

Say thanks to https://stackoverflow.com/a/58221278/6502003 for the update!

Although TypeScript and the community are in favor of this operator, until TC39 solidifies the current proposal (which at the time of this writing is at stage 1) we will have to use alternatives.

There is one alternative which gets close to optional chaining without sacrificing dev tooling: https://github.com/rimeto/ts-optchain

This article chronicles what the creators were able to achieve in trying to mirror the native chaining operator:

1. Use a syntax that closely mirrors chained property access
2. Offer a concise expression of a default value when traversal fails
3. Enable IDE code-completion tools and compile-time path validation

In practice it looks like this:

import { oc } from 'ts-optchain';

// Each of the following pairs are equivalent in result.
oc(x).a();
x && x.a;

oc(x).b.d('Default');
x && x.b && x.b.d || 'Default';

oc(x).c[100].u.v(1234);
x && x.c && x.c[100] && x.c[100].u && x.c[100].u.v || 1234;

Keep in mind that alternatives like this one will likely be unnecessary once the proposal is adopted by TypeScript.

Also, a big thanks to Ryan Cavanaugh for all the work you are doing in advocating this operator to TC39!