robmathers

var groupBy = function(data, key) { // `data` is an array of objects, `key` is the key (or property accessor) to group by
  // reduce runs this anonymous function on each element of `data` (the `item` parameter,
  // returning the `storage` parameter at the end
  return data.reduce(function(storage, item) {
    // get the first instance of the key by which we're grouping
    var group = item[key];
    
    // set `storage` for this instance of group to the outer scope (if not empty) or initialize it
    storage[group] = storage[group] || [];
    

fer-ri

import {Directive, ElementRef, Input} from '@angular/core';
 
@Directive({
    selector: '[background-image]'
})
export class BackgroundImage {
    private el: HTMLElement;

    constructor(el: ElementRef) {
        this.el = el.nativeElement;