How to efficiently calculate the angle between two points in JavaScript?

Easy way to calculate angles between two points in JavaScript

In JavaScript development, we often need to calculate the angle of one point relative to another (in radians), such as handling mouse click events. This article provides an efficient JavaScript solution.

Question: How to calculate the angle of point B relative to point A? Suppose the coordinates of points A and point B are known. Traditional trigonometric function calculation methods are more complex, but JavaScript's Math.atan2() function provides a more concise way.

The Math.atan2(y, x) function directly calculates the radian of the point relative to the origin based on the coordinates (x, y) of the point. However, we need to calculate the angle of point B relative to point A, so we need to first calculate the coordinate difference of point B relative to point A: By - Ay and Bx - Ax , and pass these two differences as parameters into Math.atan2() function.

The return value range of the Math.atan2() function is [-π, π]. In order to obtain a counterclockwise rotation angle between 0 and 2π, we need to adjust the negative radians. When the calculated radian is less than 0, adding 2π can ensure that the angle is between 0 and 2π.

The following code snippet demonstrates the functionality:

 // Calculate the counterclockwise rotation of point B relative to point A const getRadian = (B, A) => {
  let rad = Math.atan2(By - Ay, Bx - Ax);
  return rad <p> This code uses the <code>Math.atan2()</code> function and simple conditional judgment to efficiently calculate the counterclockwise rotation radian of point B relative to point A. By passing in the coordinate objects of points A and point B, the function returns a radian value between 0 and 2π, which is convenient for subsequent applications.</p>

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