如何在打字稿上使用linq js总和和平均值？

Question

I am trying to use Linq js library on the typescript. I have the following function;

 calculateAvgRating(data) {
        this.user_ratings = Enumerable.from(data).groupBy(p => '${p.rating_type}', null,
            function (key, g) {
                var result = {
                    rating_type: key,
                    total: g.sum("$.rating"),
                    avg: g.average("$.rating")
                }
                return result;
            }).toArray();
    }

However, the lines where I am calculating the total and average are giving me the following typescript error;

Argument of type 'string' is not assignable to parameter of type '(element: {}) => number'.

I know, I need to change the parameter that I am giving to sum and average functions but I couldn't figure it out.

Answer 1

It seems like the definition file for the linq.js library does not support the shorthand ( op.sum("$.value | 0") ), although the library does.

You can either exclude the ts compiler from prompting an error on the library, which is not ideal, or use function callbacks.

import { from } from 'linq';

interface IRating {
    type: number,
    value: number
};

let data: IRating[] = [{
    type: 5,
    value: 5.0
}, {
    type: 0,
    value: 1.0
}, {
    type: 3,
    value: 2.3
}, {
    type: 0,
    value: 0.6
}];


let result = from(data).groupBy(rating => rating.type, null, (key, op) => {
    return {
        type: key,
        total: op.sum(item => item["value"] || 0),
        avg: op.average(item => item["value"] || 0)
    };
}).toArray();

console.log(result)