javascript - TypeScript TS7015: Element implicitly has an 'any' type because index expression is not of type &am

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Im getting this compilation error in my Angular 2 app:

TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.

The piece of code causing it is:

getApplicationCount(state:string) {
    return this.applicationsByState[state] ? this.applicationsByState[state].length : 0;
  }

This however doesn't cause this error:

getApplicationCount(state:string) {
    return this.applicationsByState[<any>state] ? this.applicationsByState[<any>state].length : 0;
  }

This doesn't make any sense to me. I would like to solve it when defining the attributes the first time. At the moment I'm writing:

private applicationsByState: Array<any> = [];

But someone mentioned that the problem is trying to use a string type as index in an array and that I should use a map. But I'm not sure how to do that.

Thans for your help!

Im getting this compilation error in my Angular 2 app:

TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.

The piece of code causing it is:

getApplicationCount(state:string) {
    return this.applicationsByState[state] ? this.applicationsByState[state].length : 0;
  }

This however doesn't cause this error:

getApplicationCount(state:string) {
    return this.applicationsByState[<any>state] ? this.applicationsByState[<any>state].length : 0;
  }

This doesn't make any sense to me. I would like to solve it when defining the attributes the first time. At the moment I'm writing:

private applicationsByState: Array<any> = [];

But someone mentioned that the problem is trying to use a string type as index in an array and that I should use a map. But I'm not sure how to do that.

Thans for your help!

• javascript
• angular
• typescript

Share Improve this question Follow edited Oct 14, 2021 at 9:31 Erik Philips 54.6k1111 gold badges131131 silver badges155155 bronze badges asked Nov 1, 2016 at 10:40 Ole SpaarmannOle Spaarmann 16.7k2828 gold badges104104 silver badges167167 bronze badges 2

• 6 If you are trying to define a dictionary (with string keys), use type {[key: string]: any} – Harry Ninh Commented Nov 1, 2016 at 10:43
• Now I'm getting TS2339: Property 'size' does not exist on type '{ [key: string]: any; }'. when trying to get the number of elements with this.availableStates.size. – Ole Spaarmann Commented Nov 1, 2016 at 10:47

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6 Answers 6

Sorted by: Reset to default 168

If you want a key/value data structure then don't use an array.

You can use a regular object:

private applicationsByState: { [key: string]: any[] } = {};

getApplicationCount(state: string) {
    return this.applicationsByState[state] ? this.applicationsByState[state].length : 0;
}

Or you can use a Map:

private applicationsByState: Map<string, any[]> = new Map<string, any[]>();

getApplicationCount(state: string) {
    return this.applicationsByState.has(state) ? this.applicationsByState.get(state).length : 0;
}

Not the OP's direct issue but for users encountering this error for libraries not under their control, one can suppress this error is by adding:

{
  ...
  "suppressImplicitAnyIndexErrors": true,
  ...
}

to the tsconfig.json file.

---

Deprecation Notice for configurations in TypeScript v5.5.

These configurations will continue to "work" until TypeScript 5.5, at which point they will be removed entirely. In TypeScript 4.9.5+, 5.0, 5.1, 5.2, 5.3, and 5.4, you can specify ignoreDeprecations: "5.0" to silence this warning.

I used this to get around it so I could use the window object.

//in js code somewhere
window.DataManager = "My Data Manager";


//in strict typescript file
let test = (window as { [key: string]: any })["DataManager"] as string;
console.log(test); //output= My Data Manager

I was actually working with React and I got this error when I assigned an object's property through a custom key (i.e. myObj[myKey] = ). To resolve it, I simply used as keyof:

interface IMyObj { title: string; content: string; }
const myObj: IMyObj = { title: 'Hi', content: 'Hope all is well' };
const myKey: string = 'content';

myObj[myKey as keyof IMyObj] = 'All is great now!';

This explicitly tells Typescript that your custom string (myKey) belongs to the group of properties from an interface/type you used for declaring your object (myObj).

P.S.: another way to get the property's value is shown on a closed Typescript's issue on Github through extends:

interface IMyObj {
  title: string;
  content: string;
}

const myObj: IMyObj = { title: 'Hi', content: 'Hope all is well' };
const myKey: string = 'content';

const getKeyValue = <T extends object, U extends keyof T>(obj: T) => (key: U) =>
  obj[key];
console.log(getKeyValue(myObj)(myKey));

In tsconfig.json

 compilerOptions:{

  "suppressImplicitAnyIndexErrors": true,
  "strictNullChecks":false,
  "strictPropertyInitialization": false,

 }

This works for me, in tsconfig.json:

compilerOptions:{ ... "noImplicitAny": false, ... }

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