TypeScript helpers.isNumber函數代碼示例

export function containsNumber(coordinates: any[]): boolean {
    if (coordinates.length > 1 && isNumber(coordinates[0]) && isNumber(coordinates[1])) {
        return true;
    }

    if (Array.isArray(coordinates[0]) && coordinates[0].length) {
        return containsNumber(coordinates[0]);
    }
    throw new Error("coordinates must only contain numbers");
}

/**
 * Takes a {@link LineString} and returns a {@link Point} at a specified distance along the line.
 *
 * @name along
 * @param {Feature<LineString>} line input line
 * @param {number} distance distance along the line
 * @param {Object} [options] Optional parameters
 * @param {string} [options.units="kilometers"] can be degrees, radians, miles, or kilometers
 * @returns {Feature<Point>} Point `distance` `units` along the line
 * @example
 * var line = turf.lineString([[-83, 30], [-84, 36], [-78, 41]]);
 * var options = {units: 'miles'};
 *
 * var along = turf.along(line, 200, options);
 *
 * //addToMap
 * var addToMap = [along, line]
 */
function along(line: Feature<LineString>| LineString, distance: number, options: {
    units?: Units
} = {}): Feature<Point> {
    // Optional parameters
    if (!isObject(options)) throw new Error('options is invalid');

    // Validation
    let coords;
    if (line.type === 'Feature') coords = line.geometry.coordinates;
    else if (line.type === 'LineString') coords = line.coordinates;
    else throw new Error('input must be a LineString Feature or Geometry');
    if (!isNumber(distance)) throw new Error('distance must be a number');

    let travelled = 0;
    for (let i = 0; i < coords.length; i++) {
        if (distance >= travelled && i === coords.length - 1) break;
        else if (travelled >= distance) {
            const overshot = distance - travelled;
            if (!overshot) return point(coords[i]);
            else {
                const direction = bearing(coords[i], coords[i - 1]) - 180;
                const interpolated = destination(coords[i], overshot, direction, options);
                return interpolated;
            }
        } else {
            travelled += measureDistance(coords[i], coords[i + 1], options);
        }
    }
    return point(coords[coords.length - 1]);
}

/**
 * Takes a {@link FeatureCollection} of points and calculates the median center,
 * algorithimically. The median center is understood as the point that is
 * requires the least total travel from all other points.
 *
 * Turfjs has four different functions for calculating the center of a set of
 * data. Each is useful depending on circumstance.
 *
 * `@turf/center` finds the simple center of a dataset, by finding the
 * midpoint between the extents of the data. That is, it divides in half the
 * farthest east and farthest west point as well as the farthest north and
 * farthest south.
 *
 * `@turf/center-of-mass` imagines that the dataset is a sheet of paper.
 * The center of mass is where the sheet would balance on a fingertip.
 *
 * `@turf/center-mean` takes the averages of all the coordinates and
 * produces a value that respects that. Unlike `@turf/center`, it is
 * sensitive to clusters and outliers. It lands in the statistical middle of a
 * dataset, not the geographical. It can also be weighted, meaning certain
 * points are more important than others.
 *
 * `@turf/center-median` takes the mean center and tries to find, iteratively,
 * a new point that requires the least amount of travel from all the points in
 * the dataset. It is not as sensitive to outliers as `@turf/center-mean`, but it is
 * attracted to clustered data. It, too, can be weighted.
 *
 * **Bibliography**
 *
 * Harold W. Kuhn and Robert E. Kuenne, “An Efficient Algorithm for the
 * Numerical Solution of the Generalized Weber Problem in Spatial
 * Economics,” _Journal of Regional Science_ 4, no. 2 (1962): 21–33,
 * doi:{@link https://doi.org/10.1111/j.1467-9787.1962.tb00902.x}.
 *
 * James E. Burt, Gerald M. Barber, and David L. Rigby, _Elementary
 * Statistics for Geographers_, 3rd ed., New York: The Guilford
 * Press, 2009, 150–151.
 *
 * @name centerMedian
 * @param {FeatureCollection<any>} features Any GeoJSON Feature Collection
 * @param {Object} [options={}] Optional parameters
 * @param {string} [options.weight] the property name used to weight the center
 * @param {number} [options.tolerance=0.001] the difference in distance between candidate medians at which point the algorighim stops iterating.
 * @param {number} [options.counter=10] how many attempts to find the median, should the tolerance be insufficient.
 * @returns {Feature<Point>} The median center of the collection
 * @example
 * var points = turf.points([[0, 0], [1, 0], [0, 1], [5, 8]]);
 * var medianCenter = turf.centerMedian(points);
 *
 * //addToMap
 * var addToMap = [points, medianCenter]
 */
function centerMedian(
    features: FeatureCollection<any>,
    options: { weight?: string, tolerance?: number, counter?: number} = {}
): Feature<Point, {
    medianCandidates: Array<Position>,
    [key: string]: any
}> {
    // Optional params
    options = options || {};
    if (!isObject(options)) throw new Error('options is invalid');
    var counter = options.counter || 10;
    if (!isNumber(counter)) throw new Error('counter must be a number');
    var weightTerm = options.weight;

    // Calculate mean center:
    var meanCenter = centerMean(features, {weight: options.weight});

    // Calculate center of every feature:
    var centroids: any = featureCollection([]);
    featureEach(features, function (feature) {
        centroids.features.push(centroid(feature, {properties: {weight: feature.properties[weightTerm]}}));
    });

    centroids.properties = {
        tolerance: options.tolerance,
        medianCandidates: []
    };
    return findMedian(meanCenter.geometry.coordinates, [0, 0], centroids, counter);
}

export function randomLineString(count?: number, options: {
    bbox?: BBox,
    num_vertices?: number,
    max_length?: number,
    max_rotation?: number,
} = {}): FeatureCollection<LineString, any> {
    // Optional parameters
    options = options || {};
    if (!isObject(options)) { throw new Error("options is invalid"); }
    const bbox = options.bbox;
    let num_vertices = options.num_vertices;
    let max_length = options.max_length;
    let max_rotation = options.max_rotation;
    if (count === undefined || count === null) { count = 1; }

    // Default parameters
    if (!isNumber(num_vertices) || num_vertices === undefined || num_vertices < 2) { num_vertices = 10; }
    if (!isNumber(max_length) || max_length === undefined) { max_length = 0.0001; }
    if (!isNumber(max_rotation) || max_rotation === undefined) { max_rotation = Math.PI / 8; }

    const features = [];
    for (let i = 0; i < count; i++) {
        const startingPoint = randomPosition(bbox);
        const vertices = [startingPoint];
        for (let j = 0; j < num_vertices - 1; j++) {
            const priorAngle = (j === 0) ?
                Math.random() * 2 * Math.PI :
                Math.tan(
                    (vertices[j][1] - vertices[j - 1][1]) /
              (vertices[j][0] - vertices[j - 1][0]),
                );
            const angle = priorAngle + (Math.random() - 0.5) * max_rotation * 2;
            const distance = Math.random() * max_length;
            vertices.push([
                vertices[j][0] + distance * Math.cos(angle),
                vertices[j][1] + distance * Math.sin(angle),
            ]);
        }
        features.push(lineString(vertices));
    }

    return featureCollection(features);
}

export function randomPolygon(count?: number, options: {
    bbox?: BBox,
    num_vertices?: number,
    max_radial_length?: number,
} = {}): FeatureCollection<Polygon, any> {
    // Default param
    if (count === undefined || count === null) { count = 1; }
    if (!isNumber(options.num_vertices) || options.num_vertices === undefined) {
        options.num_vertices = 10;
    }
    if (!isNumber(options.max_radial_length) || options.max_radial_length === undefined) {
        options.max_radial_length = 10;
    }

    const features = [];
    for (let i = 0; i < count; i++) {
        let vertices: any[] = [];
        const circleOffsets = Array.apply(null, new Array(options.num_vertices + 1)).map(Math.random);

        // Sum Offsets
        circleOffsets.forEach((cur: any, index: number, arr: any[]) => {
            arr[index] = (index > 0) ? cur + arr[index - 1] : cur;
        });

        // scaleOffsets
        circleOffsets.forEach((cur: any) => {
            cur = cur * 2 * Math.PI / circleOffsets[circleOffsets.length - 1];
            const radialScaler = Math.random();
            vertices.push([
                radialScaler * (options.max_radial_length || 10) * Math.sin(cur),
                radialScaler * (options.max_radial_length || 10) * Math.cos(cur),
            ]);
        });
        vertices[vertices.length - 1] = vertices[0]; // close the ring

        // center the polygon around something
        vertices = vertices.map(vertexToCoordinate(randomPosition(options.bbox)));
        features.push(polygon([vertices]));
    }
    return featureCollection(features);
}

 geomEach(geojson, function (geom, featureIndex, properties) {
     let weight = properties[options.weight];
     weight = (weight === undefined || weight === null) ? 1 : weight;
     if (!isNumber(weight)) throw new Error('weight value must be a number for feature index ' + featureIndex);
     weight = Number(weight);
     if (weight > 0) {
         coordEach(geom, function (coord) {
             sumXs += coord[0] * weight;
             sumYs += coord[1] * weight;
             sumNs += weight;
         });
     }
 });

 featureEach(centroids, function (theCentroid: any) {
     var weightValue = theCentroid.properties.weight;
     var weight = (weightValue === undefined || weightValue === null) ? 1 : weightValue;
     weight = Number(weight);
     if (!isNumber(weight)) throw new Error('weight value must be a number');
     if (weight > 0) {
         centroidCount += 1;
         var distanceFromCandidate = weight * distance(theCentroid, candidateMedian);
         if (distanceFromCandidate === 0) distanceFromCandidate = 1;
         var k = weight / distanceFromCandidate;
         candidateXsum += theCentroid.geometry.coordinates[0] * k;
         candidateYsum += theCentroid.geometry.coordinates[1] * k;
         kSum += k;
     }
 });

/**
 * Converts a GeoJSON coordinates to the defined `projection`
 *
 * @private
 * @param {GeoJSON} geojson GeoJSON Feature or Geometry
 * @param {string} projection defines the projection system to convert the coordinates to
 * @param {Object} [options] Optional parameters
 * @param {boolean} [options.mutate=false] allows GeoJSON input to be mutated (significant performance increase if true)
 * @returns {GeoJSON} Converted GeoJSON
 */
function convert(geojson: any, projection: string, options: {mutate?: boolean} = {}): any {
    // Optional parameters
    options = options || {};
    var mutate = options.mutate;

    // Validation
    if (!geojson) throw new Error('geojson is required');

    // Handle Position
    if (Array.isArray(geojson) && isNumber(geojson[0])) geojson = (projection === 'mercator') ? convertToMercator(geojson) : convertToWgs84(geojson);

    // Handle GeoJSON
    else {
        // Handle possible data mutation
        if (mutate !== true) geojson = clone(geojson);

        coordEach(geojson, function (coord) {
            var newCoord = (projection === 'mercator') ? convertToMercator(coord) : convertToWgs84(coord);
            coord[0] = newCoord[0];
            coord[1] = newCoord[1];
        });
    }
    return geojson;
}