Correcting format MultiPolygons

[cbanbury]

According the the GeoJSON spec features with more than one polygon should have the type MultiPolygon rather than Polygon and be an array of polygon coordinate arrays.

Here's a code snippet for the changes made

var fs = require('fs');

var data = fs.readFileSync('cities.geojson');
data = JSON.parse(data);

data.features.forEach(item=>{
    var polygon = item.geometry.coordinates;
    
    if (polygon.length > 1) {
        item.geometry.type = 'MultiPolygon';
        
        var fixed = [];
        polygon.forEach(ring=>{
            fixed.push([ring]); // nest in additional array
        })
        
        item.geometry.coordinates = fixed;
    }
})