Math.atan2()
对于 Math.atan2(y, x)
,Math.atan2()
静态方法返回正 x 轴与从 (0, 0) 到点 (x, y) 的射线之间的平面中的角度(以弧度为单位)。
¥The Math.atan2()
static method 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)
.
Try it
语法
参数
返回值
描述
¥Description
Math.atan2()
方法测量正 x 轴和点 (x, y)
之间的逆时针角度 θ(以弧度为单位)。请注意,此函数的参数首先传递 y 坐标,然后传递 x 坐标。
¥The Math.atan2()
method measures the counterclockwise angle θ, 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.
Math.atan2()
传递单独的 x
和 y
参数,而 Math.atan()
传递这两个参数的比率。Math.atan2(y, x)
在以下情况下与 Math.atan(y / x)
不同:
¥Math.atan2()
is passed separate x
and y
arguments, while Math.atan()
is passed the ratio of those two arguments. Math.atan2(y, x)
differs from Math.atan(y / x)
in the following cases:
x |
y |
Math.atan2(y, x) |
Math.atan(y / x) |
---|---|---|---|
Infinity |
Infinity |
π / 4 | NaN |
Infinity |
-Infinity |
-π / 4 | NaN |
-Infinity |
Infinity |
3π / 4 | NaN |
-Infinity |
-Infinity |
-3π / 4 | NaN |
0 | 0 | 0 | NaN |
0 | -0 | -0 | NaN |
< 0(包括 -0 ) |
0 | π | 0 |
< 0(包括 -0 ) |
-0 | -π | 0 |
-Infinity |
0 | π | -0 |
-0 | 0 | π / 2 | -π / 2 |
-Infinity |
< 0 | -π | 0 |
-0 | < 0 | -π / 2 | π / 2 |
此外,对于第二和第三象限 (x < 0
) 中的点,Math.atan2()
将输出小于
或大于
¥In addition, for points in the second and third quadrants (x < 0
), Math.atan2()
would output an angle less than
or greater than
.
因为 atan2()
是 Math
的静态方法,所以你始终将其用作 Math.atan2()
,而不是用作你创建的 Math
对象的方法(Math
不是构造函数)。
¥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).
示例
使用 Math.atan2()
Math.atan2(y, x) 和 Math.atan(y / x) 之间的区别
¥Difference between Math.atan2(y, x) and Math.atan(y / x)
以下脚本打印在 Math.atan2(y, x)
和 Math.atan(y / x)
之间产生差异的所有输入。
¥The following script prints all inputs that produce a difference between Math.atan2(y, x)
and Math.atan(y / x)
.
const formattedNumbers = new Map([
[-Math.PI, "-π"],
[(-3 * Math.PI) / 4, "-3π/4"],
[-Math.PI / 2, "-π/2"],
[-Math.PI / 4, "-π/4"],
[Math.PI / 4, "π/4"],
[Math.PI / 2, "π/2"],
[(3 * Math.PI) / 4, "3π/4"],
[Math.PI, "π"],
[-Infinity, "-∞"],
[Infinity, "∞"],
]);
function format(template, ...args) {
return String.raw(
{ raw: template },
...args.map((num) =>
(Object.is(num, -0)
? "-0"
: formattedNumbers.get(num) ?? String(num)
).padEnd(5),
),
);
}
console.log(`| x | y | atan2 | atan |
|-------|-------|-------|-------|`);
for (const x of [-Infinity, -1, -0, 0, 1, Infinity]) {
for (const y of [-Infinity, -1, -0, 0, 1, Infinity]) {
const atan2 = Math.atan2(y, x);
const atan = Math.atan(y / x);
if (!Object.is(atan2, atan)) {
console.log(format`| ${x} | ${y} | ${atan2} | ${atan} |`);
}
}
}
输出是:
¥The output is:
| x | y | atan2 | atan | |-------|-------|-------|-------| | -∞ | -∞ | -3π/4 | NaN | | -∞ | -1 | -π | 0 | | -∞ | -0 | -π | 0 | | -∞ | 0 | π | -0 | | -∞ | 1 | π | -0 | | -∞ | ∞ | 3π/4 | NaN | | -1 | -∞ | -π/2 | π/2 | | -1 | -1 | -3π/4 | π/4 | | -1 | -0 | -π | 0 | | -1 | 0 | π | -0 | | -1 | 1 | 3π/4 | -π/4 | | -1 | ∞ | π/2 | -π/2 | | -0 | -∞ | -π/2 | π/2 | | -0 | -1 | -π/2 | π/2 | | -0 | -0 | -π | NaN | | -0 | 0 | π | NaN | | -0 | 1 | π/2 | -π/2 | | -0 | ∞ | π/2 | -π/2 | | 0 | -0 | -0 | NaN | | 0 | 0 | 0 | NaN | | ∞ | -∞ | -π/4 | NaN | | ∞ | ∞ | π/4 | NaN |
规范
Specification |
---|
ECMAScript Language Specification # sec-math.atan2 |
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