TS2488 Type must have a '[Symbol.iterator]()' method that returns an iterator. TypeScript Virtual Projects

ERROR :
TS2488 Type must have a 'Symbol.iterator' method that returns an iterator. TypeScript Virtual Project
TypeScript Version: 2.1
I am using typescript in a Visual Studio 2015

for (var item of this.listOfTemplate) { //error here

        }

tsconfig

{
  "compileOnSave ": true,
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "removeComments": true,
    "lib": [ "es5", "dom" ]
  },

  "files": [
    "app.ts"
  ]
}

you are specifying target: es6 but do not included the needed es6 built in definitions in the lib: es6.

so either change the target to be es5. or add es6 to your lib flag.

Mohamed Hegazy (@mhegazy)

I ran into this also and it took forever to find: Hoping this comment will help others find this note.

I was trying to use for ... of with an array while targeting es6 (es2015).

I solved by doing what Mohamed Hegazy (@mhegazy) said, but I just added "es2015.iterable" instead of all of es6.

keywords: typescript array symbol iterator error

I'm trying to use the spread operator in this manner:

[PAGE_LAYOUTS_FETCH]: (state, { payload, error }) => {
    return Object.assign({}, state, {
        isFetching: true,
        error,
        results: [...state.results, ...payload]
    });
},

error is on the ...payload part of the code. issue still remains with "es2015.iterable" in tsconfig.json

Make sure the type isn't nullable (have a question mark at the end of the variable name)... that caused this error for me.

This also happens with an interface that fakes a tuple:

interface Foo {
    0: string;
    1: number;
    2?: boolean; // can't have an optional member in a real tuple
}

function something([ // TS2488
    name,
    age,
    alive,
]: Foo) {

add ! to the end of the var that is being spread. E.g. [{}, ...payload!]

Hello!

I'm seeing this issue as well.

I have the following interface:

export interface TasksList {
  0: ('parallel' | 'sequential');
  [key: number]: string;
}

And I'm trying to spread it this way:

const [mode, ...taskNames] = tasksList;

// TS2488: Type 'TasksList' must have a '[Symbol.iterator]()'
// method that returns an iterator.

All I want is to define a more specific type of the first element of the array.

jshado1

I've found a working solution for cases mentioned by me, jshado1 and Mike June (@mikejune).

The type should be defined this way:

export interface TasksListSpecifics {
    0: ('parallel' | 'sequential');
}

export type TasksList = (string[] & TasksListSpecifics);

Or more compact:

export type TasksList = (string[] & {
    0: ('parallel' | 'sequential');
});

The trick is to add your more specific properties on top of array of string type (Array<string>).

I've tested it and it works great, type checking is working correctly everywhere I expect it to work.

Here's the TS Playground to test this out.

add ! to the end of the var that is being spread. E.g. [{}, ...payload!]

interface IMethods {
  post: string;
  get: string;
  patch: string;
  put: string;
  delete: string;
}

type PartialRecord<K extends keyof any, T> = Partial<Record<K, T>>;

interface IEndpoint {
  route: string;
  methods: Array<keyof IMethods>;
  middlewares: PartialRecord<keyof IMethods, any[]>;
}

...endpoint.middlewares[method] -- !works
...endpoint.middlewares[method]! --works

Can you please explain what this does, because it helped in my case.

@MrCEO63 Did you check https://stackoverflow.com/questions/42273853/in-typescript-what-is-the-exclamation-mark-bang-operator-when-dereferenci?

add ! to the end of the var that is being spread. E.g. [{}, ...payload!]

LSDJHFKSJDFKSJD was so easy, i love u

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TS2488 Type must have a '[Symbol.iterator]()' method that returns an iterator. TypeScript Virtual Projects #12707

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TS2488 Type must have a '[Symbol.iterator]()' method that returns an iterator. TypeScript Virtual Projects #12707

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mhegazy commented on Dec 7, 2016

ricklove commented on Jun 22, 2017

mikejune commented on Sep 19, 2017

IAmCoder commented on Apr 27, 2018

JakobJingleheimer commented on Jun 20, 2018

chicken-suop commented on Jan 8, 2020

slavafomin commented on Feb 6, 2020

slavafomin commented on Feb 6, 2020

AllStackDev1 commented on May 18, 2020

chicken-suop commented on Jun 25, 2020

rileydev23 commented on Sep 20, 2022

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