Troubleshooting Angular2 Error: Incompatibility with TypeScript - Unable to Assign String

While working on creating a custom pipe in Angular2 for filtering, I encountered the following build error:

Error TS2322: Build: Type '() => string' is not assignable to type 'string'

Below is my sample code:

import { PipeTransform, Pipe } from 'angular2/core';
import { IProduct } from './products';

@Pipe({
name: 'productFilter'
})

export class ProductFilterPipe implements PipeTransform {
 transform(value: IProduct[], args: string[]): IProduct[] {
    let filter: string = args[0].toLocaleLowerCase ?    args[0].toLocaleLowerCase : null;
    return filter ? value.filter((product: IProduct) =>
        product.productName.toLocaleLowerCase().indexOf(filter) != -1) :   value;
}
}

The above-mentioned error occurs at this line of code:

let filter:

Being new to typescript, I am seeking assistance in resolving this issue. Can anyone help me with fixing this problem?

Answer №1

Make sure to include parentheses when calling the toLocaleLowerCase function. Instead of just writing toLocaleLowerCase, it should be written as toLocaleLowerCase()

If you don't include the parentheses, you're not actually executing the function. You're assigning the variable filter to the function itself rather than the result of the function after it has been called.

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