utility.js

// remove all occurences of elem from array
// if comp function gets passed in, use that for comparison
Array.prototype.remove = function(elem, comp) {
    if (comp === undefined)
        comp = (e1, e2) => e1 === e2;

    for (var i = this.length - 1; i >= 0; i--) {
        if (comp(this[i], elem)) {
            this.splice(i, 1);
        }
    }
    return this;
}
Array.prototype.flatMap = function(lambda) { 
    return Array.prototype.concat.apply([], this.map(lambda));
};


class Vector {
    constructor(x, y) {
        this.x = x;
        this.y = y;
    }
    // angle in degrees
    static fromPolar(length, angle) {
        var x = length * Math.cos(angle / 180 * Math.PI);
        var y = length * Math.sin(angle / 180 * Math.PI);
        return new Vector(x, y);
    }
    clone() {
        return new Vector(this.x, this.y);
    }
    eq(p) {
        return this.x === p.x && this.y === p.y;
    }
    plus(p) {
        return new Vector(this.x + p.x, this.y + p.y);
    }
    minus(p) {
        return new Vector(this.x - p.x, this.y - p.y);
    }
    times(factor) {
        return new Vector(this.x * factor, this.y * factor);
    }
    div(factor) {
        return new Vector(this.x / factor, this.y / factor);
    }
    length() {
        return Math.sqrt(this.x*this.x + this.y*this.y);
    }
    // angle to x-axis in degrees
    angle() {
        return Math.atan2(this.y, this.x) / Math.PI * 180;
    }
    // returns the closest point to this
    // null if no points
    closestPoint(points) {
        var minDist = Infinity;
        var minPoint = null;
        for (var i = 0; i < points.length; i++) {
            var dist = this.minus(points[i]).length();
            if (dist <= minDist) {
                minDist = dist;
                minPoint = points[i];
            }
        }
        return minPoint;
    }
}

// to generate unique ids to identify objects in d3.js data joins
Object.next_uniqueid = 1;
Object.id = function(o) {
    if (typeof o.__uniqueid === "undefined") {
        Object.defineProperty(o, "__uniqueid", {
            value: Object.next_uniqueid++,
            enumerable: false,
            writable: false
        });
    }
    return o.__uniqueid;
};