y
该属性在用户坐标系统中标识了一个 y 轴坐标。本坐标的确切效果依赖于每个元素。大多数时候，它体现了引用元素的矩形区域的左上角的 y 轴坐标（请阅读每个元素的文档以了解例外情况）。
如果没有指定这个属性，效果相当于值被设置为0，除了<filter>元素以及<mask>元素；这两个元素的y默认值为**-10%**。
用法
| 类别 | 无 |
|---|---|
| 值 | <coordinate> |
| 可变性 | Yes |
- <coordinate>
-
A <coordinate> is a length in the user coordinate system that is the given distance from the origin of the user coordinate system along the relevant axis (the x-axis for X coordinates, the y-axis for Y coordinates). Its syntax is the same as that for <length>.
Within the SVG DOM, a <coordinate> is represented as an
SVGLengthor anSVGAnimatedLength.