Javascript [Electronic resources] : The Definitive Guide (4th Edition)

Availability

JavaScript 1.0; JScript 1.0; ECMAScript v1

Synopsis

Math.atan2(y, x)

Arguments

y

The Y-coordinate of the point.

x

The X-coordinate of the point.

Returns

A value between - and radians that specifies the counterclockwise angle between the positive X-axis and the point (x, y).

Description

The Math.atan2( ) function computes the arc tangent of the ratio y/x. The y argument can be considered the Y-coordinate (or "rise") of a point, and the x argument can be considered the X-coordinate (or "run") of the point. Note the unusual order of the arguments to this function: the Y-coordinate is passed before the X-coordinate.