Get the angle between 3 coordinates (x, y, z) in 3D space

AngleBetween3PointsIn3DSpace.js

/**
 * Calculate angle between 3 points in 3D space.
 * Note: assumes we want 1 vector to run from coord1 -> coord2, and the other
 * from coord3 -> coord2.
 *
 * @param {x: number; y: number; z: number} coord1 1st (3D) coordinate
 * @param {x: number; y: number; z: number} coord2 2nd (3D) coordinate
 * @param {x: number; y: number; z: number} coord3 3rd (3D) coordinate
 *
 * @return {number} Angle between the 3 points
 */
const angleBetween3DCoords = (coord1, coord2, coord3) => {
    // Calculate vector between points 1 and 2
    const v1 = {
        x: coord1.x - coord2.x,
        y: coord1.y - coord2.y,
        z: coord1.z - coord2.z,
    };

    // Calculate vector between points 2 and 3
    const v2 = {
        x: coord3.x - coord2.x,
        y: coord3.y - coord2.y,
        z: coord3.z - coord2.z,
    };

    // The dot product of vectors v1 & v2 is a function of the cosine of the
    // angle between them (it's scaled by the product of their magnitudes).

    // Normalize v1
    const v1mag = Math.sqrt(v1.x * v1.x + v1.y * v1.y + v1.z * v1.z);
    const v1norm = {
        x: v1.x / v1mag,
        y: v1.y / v1mag,
        z: v1.z / v1mag,
    };

    // Normalize v2
    const v2mag = Math.sqrt(v2.x * v2.x + v2.y * v2.y + v2.z * v2.z);
    const v2norm = {
        x: v2.x / v2mag,
        y: v2.y / v2mag,
        z: v2.z / v2mag,
    };

    // Calculate the dot products of vectors v1 and v2
    const dotProducts = v1norm.x * v2norm.x + v1norm.y * v2norm.y + v1norm.z * v2norm.z;

    // Extract the angle from the dot products
    const angle = (Math.acos(dotProducts) * 180.0) / Math.PI;

    // Round result to 3 decimal points and return
    return Math.round(angle * 1000) / 1000;
};

// Usage:

angleBetween3DCoords({x: 1, y: 0, z: 0}, {x: 0, y: 0, z: 0}, {x: 0, y: 1, z: 0});
// => 90