Property 'replace' does not exist on type 'string'

Question

I get a strange error TS2339: Property 'X' does not exist on type 'Y'. How can I fix this?

I have added libraries to my 'tsconfig.jsonc' file:

"compilerOptions": {
    "target": "es3", // "es3" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */,
    "watch": true,
    "module": "commonjs" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */,
    "lib": [
      "esnext",
      "es2018",
      "es2017",
      "es2016",
      "es2015",
      "es7",
      "es6",
      "es5",
      "dom",
      "dom.iterable",
      "ScriptHost"
    ] /* Specify library files to be included in the compilation. */,
...
}

The code

const userName: string = groupAddress.replace('@gmail.com', '')

returns the error

Property 'replace' does not exist on type 'string'.

Similarly,

const addMembers = (email: string, studio: string, role): void => {
  const memberKey = email.trim()

returns

Property 'trim' does not exist on type 'string'.

  const groupKeys: string[] = [
    `report.${name}@gmail.com`,
    `support.${name}@gmail.com`
  ]
  groupKeys.forEach((groupKey: string) => {
    if (!GroupsApp.getGroupByEmail(groupKey).hasUser(memberKey)) {
      AdminDirectory.Members.insert({ email: memberKey, role }, groupKey)
    }
  })

returns

Property 'forEach' does not exist on type '{}'.

I expect

• the type string has the method 'replace', and
• the type string[] has the method 'forEach'.

But typescript says they do not.

Answer 1

You are targeting es3, but have told TS that it has all the libraries for up to bleeding edge available to it. Without polyfills, this is a really bad idea.

TS will NOT functionally polyfill. It only adds syntactical polyfills. So you are setting a trap for yourself. Remove the lib entries, update your target to a modern target, or add in polyfills for everything there.

Also, as mentioned, I hope you tsconfig is tsconfig.json, and not tsconfig.jsonc. Otherwise that is your issue.