Demo using newer ecmascript features to calculate angle and direction from a set of coordinates

normalizedAngleVectorDemo.js

class Vector {
	constructor(a, b) {
		if (a instanceof Point && b instanceof Point) {
			this.x = b.x - a.x;
			this.y = b.y - a.y;
			this.z = b.z - a.z;
		}
		else {
			this.x = a || 0;
			this.y = b || 0;
			this.z = z || 0;
		}
	}
}

class Point {
	constructor(x, y, z) {
		this.x = x || 0;
		this.y = y || 0;
		this.z = z || 0;
	}
}


function radToDeg(radVal) {

	return radVal * 180 / Math.PI;
}


const testCoordSet = [
	[-114.946645, 48.068177],
	[-114.962833, 48.068179],
	[-114.962799, 48.061004],
	[-114.957446, 48.06105],
	[-114.957454, 48.064635],
	[-114.946694, 48.064577]
];

// Generate our test set of points - using map because we need to return a new collection
const testPts = testCoordSet.map(coord => new Point(...coord));
console.log(testPts);

const overallRunTimeStart = performance.now();


// Using forEach because we're not returning anything. In practice, further
//  operations could benefit from map because we can chain
testPts.forEach((pt, index, array) => {

	console.log(`\r\n${index}`);

	const pointA = array[index === 0 ? array.length - 1 : index - 1]; // If at beginning, left is the last point in the array
	const pointB = pt;
	const pointC = array[index === array.length - 1 ? 0 : index + 1]; // If at end, right is the first point in the array

	const vectorAB = new Vector(pointA, pointB);
	const vectorCB = new Vector(pointC, pointB);

	console.log("vectorAB:", vectorAB);
	console.log("vectorCB:", vectorCB);

	// Stay in radians until the final result is calculated
	const absAngleABRad = Math.atan2(vectorAB.y, vectorAB.x);
	console.log(`absAngleABRad: ${absAngleABRad}`);

	const absAngleCBRad = Math.atan2(vectorCB.y, vectorCB.x);
	console.log(`absAngleCBRad: ${absAngleCBRad}`);

	const angularDiffRad = absAngleABRad - absAngleCBRad;
	console.log(`angularDiffRad: ${angularDiffRad}`);

	const angularDiffRadNormalized = Math.atan2(Math.sin(angularDiffRad), Math.cos(angularDiffRad));
	console.log(`angularDiffRadNorm: ${angularDiffRadNormalized}`);

	const angleDeg = radToDeg(angularDiffRadNormalized);
	console.warn(`angleDeg: ${angleDeg}`);
});

// old school
//for (let i = 0; i < testPts.length; i++) {

//	console.log(`\r\n${i}`);

//	const pointA = testPts[i === 0 ? testPts.length - 1 : i - 1]; // If at beginning, left is the last point in the array
//	const pointB = testPts[i];
//	const pointC = testPts[i === testPts.length - 1 ? 0 : i + 1]; // If at end, right is the first point in the array

//	const vectorAB = new Vector(pointA, pointB);
//	const vectorCB = new Vector(pointC, pointB);

//	console.log("vectorAB:", vectorAB);
//	console.log("vectorCB:", vectorCB);

//	// Stay in radians until the final result is calculated
//	const absAngleABRad = Math.atan2(vectorAB.y, vectorAB.x);
//	console.log(`absAngleABRad: ${absAngleABRad}`);

//	const absAngleCBRad = Math.atan2(vectorCB.y, vectorCB.x);
//	console.log(`absAngleCBRad: ${absAngleCBRad}`);

//	const angularDiffRad = absAngleABRad - absAngleCBRad;
//	console.log(`angularDiffRad: ${angularDiffRad}`);

//	const angularDiffRadNormalized = Math.atan2(Math.sin(angularDiffRad), Math.cos(angularDiffRad));
//	console.log(`angularDiffRadNorm: ${angularDiffRadNormalized}`);

//	const angleDeg = radToDeg(angularDiffRadNormalized);
//	console.warn(`angleDeg: ${angleDeg}`);
//}


const overallRuntimeEnd = performance.now();

console.log(`Overall run took ${overallRuntimeEnd - overallRunTimeStart} milliseconds.`);