How I Built an Interactive Map from Scratch

July 29, 2019

The other day I needed to complete a task for a client, this task consisted of creating an interactive map based on a static SVG. In this article, I’ll explain how I accomplished the job 👌

Build your map

Photo by Andrew Stutesman on Unsplash

First things first

The problem was that the map used wasn’t interactive at all, to show the selected regions you needed to add CSS classes, and there could be only one selected region at one time. So I searched the Internet for maybe one angular library that could fit my needs, but, unfortunately, without results 😢

Let’s create a new Angular lib

So I said to myself: Why not create a new library yourself? and that was it, I opened up my terminal and I typed

ng new lib @daudr/interactive-italy

(Yes, I started this project with only Italy in mind, but interchangeable maps are coming, stay tuned! 😉)

Create the main component

So I started creating the main component of the library, interactive-italy.component.ts, but what’s really is this component? The answer is simpler than you think, firstly I had to find the right SVG image, and being a noob in all of that I decided to look upon the Internet and I found just what I needed:

Italy map with regions

Thanks Wikimedia ❤

The only problem was the map wasn’t interactive.

<svg
  width="460.30981"
  height="562.58575"
>
  <path
  *ngFor="let region of regions"
  [attr.d]="region.d"
  [attr.title]="region.title"
  (click)="onRegionClick(region.title)"
  [ngClass]="{ selected: region.title | selected: selectedRegions }"
  />
</svg>

It’s all here, just that.

Create the data

But let’s find out what powers it: The regions object represents an array that contains all the regions of the map as SVG’s paths

export const REGIONS: Region[] = [
  {
    d:
      'm 374.27021,304.03051 1.36,6.34 2.24,5.51 6.27,11.18 7.01,7.71 8.24,6.15 0.87,2.33 3.67,3.53 0.33,1.35 5.56,3.7 5.16,1.83 0.21,4.85 3.43,2.43 0,0 -1.17,1.85 0.91,0.84 -2.84,1.96 -2.3,2.84 -0.82,3.1 -2.36,1.66 -1.72,3.73 -4.76,5.13 -2.04,-0.37 0.79,-0.64 -1.07,-4.29 -1.1,-1.07 -2.44,-1.62 -1.05,1.32 -0.57,-0.22 -0.98,-2.19 -1.24,0.13 -0.94,-1.26 -2.91,2.38 -1.43,2.22 -2.22,0.15 -0.42,0.9 1.25,3.55 1.52,0.89 -0.42,1.03 -0.85,-0.13 -0.25,-1.01 -0.67,1.24 -1.99,0.05 -0.63,2.64 -0.79,-2.07 -1.16,0.09 -0.87,2.4 -1.33,0.05 -0.28,1.46 -1.87,-0.98 -2.1,0.52 0,0 -2.49,-3.27 -1.96,0.19 -2.4,-1.41 -1.03,0.65 -1.33,-0.4 -1.75,-3.31 -1.32,0.73 -1.07,-1.18 -1.78,-0.49 -1.06,2.09 -4.05,1.35 -1.48,-0.93 -0.73,-1.81 -1.84,-0.43 -1.48,-1.43 -1.73,-0.7 -1.4,1.36 -1,-3.63 1.28,-2.29 -1,-1.41 -1.01,0.18 -1.98,-2.28 -0.9,0.37 -7.65,-4.49 -2.03,-0.72 -0.02,1.24 -2.38,-0.64 -1.41,-2.25 0.15,-4.92 0.78,0.36 2.08,-1.78 0.05,-2.39 1.73,-0.13 6.56,3.53 1.24,-0.77 1.69,0.62 1.07,-2.23 1.5,-0.29 -0.53,-0.71 1.83,-0.33 -1.93,-1.22 -0.3,-1.63 -2.43,-0.84 -2.58,-2.54 -0.65,-3.28 -3.74,-2.48 2.08,-2.33 -3.99,-3.74 3.18,-2.42 -0.1,-2.38 -1,-1.86 1.03,-0.58 0.76,-2.76 2.75,1.04 0.61,-0.73 1.35,0 0.58,0.98 1.5,-0.77 2.26,0.31 1.35,-1.17 0.76,-3.43 -1.99,-0.63 -1.15,-1.37 0.54,-1.68 0,0 0,0 0,0 0,0 0,0 1.66,0.48 1.88,-1.33 0.57,0.46 0.6,-2.37 2.37,-0.39 0.3,-2.49 1.34,-1.49 0.24,-1.44 2.08,1.13 2.37,-1.11 0.67,0.94 1.35,-0.17 2.01,-0.94 0.46,-2.21 0.68,-0.38 2.78,-0.18 2.11,-1.41 4.99,-1.07 0,0 z',
    title: 'Abruzzo'
  },
  {
    d:
      'm 457.43021,430.14051 -0.33,-1.23 1.34,-1.23 1.95,-0.38 4.65,0.78 2.51,-0.9 1.45,1.05 1.69,-0.91 -0.16,-0.95 1.67,-0.43 -0.18,-0.76 0.82,0.29 1.42,-0.85 2.3,1.65 1.74,0.3 0.24,1.03 1.26,0.3 0.61,2.35 0.62,-0.42 1.84,1.5 -0.64,1.04 0.3,1.55 -1.79,2.05 -1.51,-0.27 0.61,1.13 5.59,2.38 1.59,1.51 2.14,-1.96 2,0.65 2.94,6.46 6.56,6.05 0.78,1.74 1.53,0.42 3.48,-4.04 2.04,2.47 -0.06,-1.89 0.97,-0.26 0.85,1.33 0.11,-1.74 1.69,0.73 1.01,-0.64 0.17,0.99 1.17,0.7 0.54,-0.74 2.92,2.22 -1.03,0.51 1.22,1.41 -0.9,3.62 0.92,2.05 -0.63,0.46 -0.43,2.89 0.96,1.01 -0.44,0.81 1.16,0.88 -0.96,2.08 0.86,0.94 1.7,-0.43 1.77,1.07 0.37,1.62 1.74,1.47 0.78,1.86 0,0 -3.94,5.64 -4.81,10.36 -2.29,1.67 0,0 -2.72,-0.95 -3.12,0.97 -3.08,-1.02 -1.91,0.37 -0.66,-1.11 -0.63,1.47 0.22,2.84 -1.03,2.22 0.26,2 -3.05,5.44 1.11,1.14 -0.44,1.32 -2.14,-2.39 -2,-0.18 -2.93,0.66 -0.02,1.75 -2.78,-1.27 -1.04,1.08 -4.8,0.26 -1.55,-1.74 0.37,-0.62 -0.85,-1.6 1.24,-2.23 -1.16,-0.32 -1.49,0.85 -0.69,-0.96 -1.85,-0.3 -1.43,1.23 -0.62,-0.87 -0.93,0.49 -0.9,-0.94 -1.68,0.18 -2.35,2.53 -0.95,2.6 0,0 -1.79,-3.55 -2.1,-1.92 -0.14,-1.48 -1.68,-0.98 0,0 1.69,-1.01 -1.27,-1.38 1.21,-0.34 1.56,-2.12 -0.32,-2.91 1.62,-1.65 -0.14,-1 3.47,-1.48 -0.52,-1.23 0.93,-0.83 -0.04,-1.42 -0.61,-1.15 -2.93,-0.85 -0.14,-1.32 -1.64,-1.51 -0.05,-2.56 -2.1,-0.76 -1.6,-2.14 -2.06,-1.03 -0.48,-1.73 -2.17,-1.71 0.72,-1.08 -1.35,-3.21 0.7,-0.82 -4.35,-2.63 0.73,-2.02 1.65,-1.01 0.06,-0.81 -5.93,-3.85 0.17,-4.85 -0.82,-0.07 0.22,-1.18 -2.06,-1.27 2.1,-0.15 0.12,-2.14 -1.02,-0.52 0.43,-0.66 4.79,1.08 0.64,-0.35 -0.23,-1.16 2.96,-1.29 2.26,-5.87 z',
    title: 'Basilicata'
  },
  ...
]

And then comes the logic behind all

If we add some logic we have our full component

export class InteractiveItalyComponent {
  public regions = REGIONS;
  public selectedRegions: string[] = [];

  @Output() regionsChange = new EventEmitter<string[]>();

  onRegionClick(region: string) {
    const index = this.selectedRegions.indexOf(region);
    index === -1 ? this.selectedRegions.push(region) : this.selectedRegions.splice(index, 1);

    this.regionsChange.emit(this.selectedRegions);
  }
}

But don’t forget the utilities

I just added a pipe to know if a region has been selected:

export class SelectedPipe implements PipeTransform {
  transform(value: string, regions: string[]): boolean {
    return regions.indexOf(value) !== -1;
  }
}