Multiple tsconfig.json issue with commonJS for node.js and es6 for reactjs

My current folder structure for typescript:

ts_dev
--client
  *components.tsx
  *tsconfig.json

--server
  *server.ts
  *tsconfig.json
  --share
    *utility.ts

The Node.js server needs to use commonjs modules, and es2015 for the client side components. I place the share folder used by both client and server under the server directory because it needs commonJS for Node.js.

tsconfig.json in server:

{
  "compilerOptions": {
    "module": "commonJS",
    "target": "es2015",
    "moduleResolution": "node",
    "outDir": "../../src",
    "lib": ["es6", "dom"],
    "types": ["reflect-metadata","system"],
    "jsx": "react"
  },
  "exclude": [
    "node_modules",
  ]
}

tsconfig.json in client:

{
  "compilerOptions": {
    "module": "es2015",
    "target": "es2015",
    "moduleResolution": "node",
    "outDir": "../../src",
    "lib": ["es6", "dom"],
    "types": ["reflect-metadata","system"],
    "jsx": "react"
  },
  "exclude": [
    "node_modules",
  ]
}

However I find that the scripts in share are always complied in es6 (Use export,import etc) instead of commonJS, which breaks my server. I suspect it's caused by the tsconfig in the client. What can I do to fix this issue?