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TypeError: [object Object] is not iterable!↵ at push../node_modules/@babel/runtime-corejs2/node_modules/core-js/library/modules/_for-of.js.module.exports #11180

juansalvatore opened this issue Feb 27, 2020 · 5 comments


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@juansalvatore juansalvatore commented Feb 27, 2020

Bug Report

  • I would like to work on a fix!

Current Behavior
A clear and concise description of the behavior.
I'm getting the following error after upgrading to next v9:

"TypeError: [object Object] is not iterable!
    at push../node_modules/@babel/runtime-corejs2/node_modules/core-js/library/modules/_for-of.js.module.exports (http://localhost:3000/_next/static/runtime/main.js?ts=1582833143367:1602:42)
    at http://localhost:3000/_next/static/runtime/main.js?ts=1582833143367:1326:34
    at new Map (http://localhost:3000/_next/static/development/pages/searchPage.js?ts=1582833143367:24950:34)
    at regionsReducer (http://localhost:3000/_next/static/development/pages/_app.js?ts=1582833143367:227410:30)
    at combination (http://localhost:3000/_next/static/development/pages/searchPage.js?ts=1582833143367:172965:29)
    at p (<anonymous>:1:36402)
    at v (<anonymous>:1:36684)
    at <anonymous>:1:40069
    at Object.dispatch (http://localhost:3000/_next/static/development/pages/searchPage.js?ts=1582833143367:172719:22)
    at e (<anonymous>:1:40553)
    at http://localhost:3000/_next/static/development/pages/_app.js?ts=1582833143367:182911:16
    at dispatch (http://localhost:3000/_next/static/development/pages/searchPage.js?ts=1582833143367:173144:28)
    at http://localhost:3000/_next/static/development/pages/searchPage.js?ts=1582833143367:212336:9"

Input Code

  • REPL or Repo link if applicable:
    We have this code.
      const fetchedRegions = new Map(state.fetchedRegions)

Expected behavior/code
A clear and concise description of what you expected to happen (or code).

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

  • Filename: babel.config.js
  "presets": ["next/babel"],
  "plugins": [
        "absoluteRuntime": false,
        "corejs": false,
        "helpers": true,
        "regenerator": true,
        "useESModules": false,
        "version": "7.0.0-beta.0"
    ["styled-components", { "ssr": true, "pure": true }],
        "libraryName": "@material-ui/core",
        "libraryDirectory": "",
        "camel2DashComponentName": false
        "libraryName": "@material-ui/icons",
        "libraryDirectory": "",
        "camel2DashComponentName": false
  "env": {
    "test": {
      "presets": [["next/babel", { "preset-env": { "modules": "commonjs" } }]]


npx: installed 1 in 1.124s

    OS: macOS 10.15.3
    Node: 12.13.1 - /usr/local/bin/node
    Yarn: 1.21.1 - /usr/local/bin/yarn
    npm: 6.12.1 - /usr/local/bin/npm
    @babel/core: ^7.8.6 => 7.8.6 
    @babel/plugin-transform-runtime: ^7.8.3 => 7.8.3 
    babel-eslint: ^10.1.0 => 10.1.0 
    babel-jest: ^24.1.0 => 24.9.0 
    babel-loader: ^8.0.5 => 8.0.6 
    babel-plugin-import: ^1.12.2 => 1.13.0 
    babel-plugin-module-resolver: ^3.2.0 => 3.2.0 
    babel-plugin-root-import: ^5.1.0 => 5.1.0 
    babel-plugin-styled-components: ^1.10.7 => 1.10.7 
    babel-runtime: ^6.26.0 => 6.26.0 
    eslint: ^6.8.0 => 6.8.0 
    eslint-import-resolver-babel-plugin-root-import: ^1.1.1 => 1.1.1 
    jest: ^24.1.0 => 24.9.0 

Possible Solution

I'm not sure if we need to upgrade some dependency or we need a polyfill. It's weird that after upgrading from next js 8 to 9 we get this issue.

Additional context/Screenshots
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@babel-bot babel-bot commented Feb 27, 2020

Hey @juansalvatore! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."


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@nicolo-ribaudo nicolo-ribaudo commented Feb 27, 2020

Can you add console.log(Symbol.iterator in state.fetchedRegions, state.fetchedRegions, state.fetchedRegions[Symbol.iterator])?


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@ethanryan ethanryan commented Feb 27, 2020

hi @nicolo-ribaudo, thanks for your quick response.

i'm working on this with @juansalvatore.

console.logging that logs:

{fetchedRegions: Map, boroughTree: Array(0)}


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@JLHwung JLHwung commented Feb 27, 2020

Can you log the constructor of the state.fetchedRegions?


I doubt that state.fetchedRegions is not constructed from the builtin Map.


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@ethanryan ethanryan commented Feb 27, 2020

may have misunderstood your question.

i'm doing:

console.log('qqq0 - state.fetchedRegions.constructor', state.fetchedRegions.constructor)
console.log('qqq1 - Symbol.iterator in state.fetchedRegions: ', Symbol.iterator in state.fetchedRegions)
console.log('qqq2 - state.fetchedRegions: ', state.fetchedRegions)
console.log('qqq3 - state.fetchedRegions[Symbol.iterator]', state.fetchedRegions[Symbol.iterator])`

in the browser:


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