groupBy.pipe.ts

import { Pipe } from "angular2/core";

@Pipe({
    name: "groupBy"
})

export class groupByPipe {
    
    transform( collection: Object[] , term: string ) {

        var newValue = [];

        for (let i = 0; i < collection.length; i++) {
            let keyVal = groupByPipe.deepFind(collection[i], term);
            let index = newValue.findIndex( myObj => myObj.key == keyVal);
            if (index >= 0) {
                newValue[index].value.push(collection[i]);
            } else {
                newValue.push({key: keyVal, value: [collection[i]]});
            }
        }

        return newValue;

    }

    static deepFind(obj, path) {

        var paths = path.toString().split(/[\.\[\]]/);
        var current = obj;

        for (let i = 0; i < paths.length; ++i) {
            if (paths[i] !== "") {
                if (current[paths[i]] == undefined) {
                    return undefined;
                } else {
                    current = current[paths[i]];
                }
            }
        }
        return current;

    }

}