Øle Bjarnstroem Øle Bjarnstroem - 1 month ago 4
TypeScript Question

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

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!

Answer

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;
}
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