JavaScript - Math.atan2() method example
The Math.atan2()
function returns the angle in radians in the range -Math.PI/2
to +Math.PI/2
between the positive x-axis and the ray to the point (x, y) ≠ (0, 0).
// ONLINE-RUNNER:browser;
// y x angle in radians
console.log( Math.atan2( 2, 4) ); // 0.4636476090008061 <- ~26.6 degrees
console.log( Math.atan2( 4, -2) ); // 2.0344439357957027 <- ~116.6 degrees
console.log( Math.atan2(-2, -4) ); // -2.6779450445889870 <- ~-153.4 degrees
console.log( Math.atan2(-4, 2) ); // -1.1071487177940904 <- ~-63.4 degrees
atan2()
method has been visualised on below image:

1. Documentation
Syntax | Math.atan2(y, x) |
Parameters | y , x - integer or float number values that are coords of point (primitive value). |
Result |
Where:
If point is in 1st (I) or 2nd (II) quadrant angle is measured in counterclockwise direction. If point is in 3rd (III) or 4th (IV) quadrant angle is measured in clockwise direction.
|
Description |
|
2. Working with degrees
// ONLINE-RUNNER:browser;
function calculateAngle(y, x) {
var angle = Math.atan2(y, x);
return (180 / Math.PI) * angle; // rad to deg conversion
}
// Example usage:
console.log( calculateAngle( 2, 4) ); // 26.56505117707799 degrees
console.log( calculateAngle( 4, -2) ); // 116.56505117707799 degrees
console.log( calculateAngle(-2, -4) ); // -153.43494882292200 degrees
console.log( calculateAngle(-4, 2) ); // -63.43494882292201 degrees
3. Conversion to only clockwise angles in degrees
This section shows how to convert angles to clockwise angles (from 0 to 360 degrees).
// ONLINE-RUNNER:browser;
function calculateAngle(y, x) {
var angle = Math.atan2(y, x);
if (angle < 0.0) {
angle += 2.0 * Math.PI;
}
return (180 / Math.PI) * angle; // rad to deg conversion
}
// Example usage:
console.log( calculateAngle( 2, 4) ); // 26.56505117707799 degrees
console.log( calculateAngle( 4, -2) ); // 116.56505117707799 degrees
console.log( calculateAngle(-2, -4) ); // 206.56505117707800 degrees
console.log( calculateAngle(-4, 2) ); // 296.56505117707800 degrees
4. Conversion to only counterclockwise angles in degrees
This section shows how to convert angles to counterclockwise angles (from -360 to 0 degrees).
// ONLINE-RUNNER:browser;
function calculateAngle(y, x) {
var angle = Math.atan2(y, x);
if (angle > 0.0) {
angle -= 2.0 * Math.PI;
}
return (180 / Math.PI) * angle; // rad to deg conversion
}
// Example usage:
console.log( calculateAngle( 2, 4) ); // -333.434948822922 degrees
console.log( calculateAngle( 4, -2) ); // -243.434948822922 degrees
console.log( calculateAngle(-2, -4) ); // -153.434948822922 degrees
console.log( calculateAngle(-4, 2) ); // -63.4349488229220 degrees