我們的志工尚未將本文翻譯為 正體中文 (繁體) 版本。加入我們,幫忙翻譯!
您也可以閱讀本文的 English (US) 版本。

The Math.atan2() function returns the angle in the plane (in radians) between the positive x-axis and the ray from (0,0) to the point (x,y), for Math.atan2(y,x).

Syntax

Math.atan2(y, x)

Parameters

y
The y coordinate of the point.
x
The x coordinate of the point

Return value

The angle in radians (in [-π,π][-\pi, \pi]) between the positive x-axis and the ray from (0,0) to the point (x,y).

Description

The Math.atan2() method returns a numeric value between -π and π representing the angle theta of an (x, y) point. This is the counterclockwise angle, measured in radians, between the positive X axis, and the point (x, y). Note that the arguments to this function pass the y-coordinate first and the x-coordinate second.

A simple diagram showing the angle returned by atan2(y, x)

Math.atan2() is passed separate x and y arguments, and Math.atan() is passed the ratio of those two arguments.

Because atan2() is a static method of Math, you always use it as Math.atan2(), rather than as a method of a Math object you created (Math is not a constructor).

Examples

Using Math.atan2()

Math.atan2(90, 15); // 1.4056476493802699
Math.atan2(15, 90); // 0.16514867741462683

Math.atan2(±0, -0);               // ±PI.
Math.atan2(±0, +0);               // ±0.
Math.atan2(±0, -x);               // ±PI for x > 0.
Math.atan2(±0, x);                // ±0 for x > 0.
Math.atan2(-y, ±0);               // -PI/2 for y > 0.
Math.atan2(y, ±0);                // PI/2 for y > 0.
Math.atan2(±y, -Infinity);        // ±PI for finite y > 0.
Math.atan2(±y, +Infinity);        // ±0 for finite y > 0.
Math.atan2(±Infinity, x);         // ±PI/2 for finite x.
Math.atan2(±Infinity, -Infinity); // ±3*PI/4.
Math.atan2(±Infinity, +Infinity); // ±PI/4.

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262)
The definition of 'Math.atan2' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Math.atan2' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Math.atan2' in that specification.
Draft  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes1 Yes Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes4 Yes Yes Yes

See also

文件標籤與貢獻者

最近更新: henrywoody,