The DOMPointInit dictionary's x property is used to specify the x component of a point in 2D or 3D space when either creating or serializing a DOMPoint or DOMPointReadOnly.
In general, positive values x mean to the right, and negative values of x means to the left, assuming that transforms have not altered the orientation of the axes.
var DOMPointInit = {
  x: xPos
};
DOMPointInit.x = xPos;
var xPos = DOMPointInit.x; A double-precision floating-point value indicating the point's x coordinate. This value is unrestricted, meaning that it is allowed to be infinite or invalid (that is, its value may be NaN or ±Infinity).
If this property is missing when the DOMPointInit object is passed into fromPoint(), the value is assumed to be 0 by default.
DOMPointInit is used as an input when calling either DOMPointReadOnly.fromPoint() or DOMPoint.fromPoint(), and is returned by the DOMPointReadOnly.toJSON() and DOMPoint.toJSON() methods.
| Specification | Status | Comment | 
|---|---|---|
| Geometry Interfaces Module Level 1 The definition of 'x' in that specification.  |  Candidate Recommendation | Initial definition | 
| Desktop | ||||||
|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | |
| Basic support | ? | No | 62 | No | ? | No | 
| Mobile | |||||||
|---|---|---|---|---|---|---|---|
| Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
| Basic support | ? | ? | No | 62 | ? | No | ? | 
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    https://developer.mozilla.org/en-US/docs/Web/API/DOMPointInit/x