JavaScript get window X/Y position for scroll

The method jQuery (v1.10) uses to find this is:

var doc = document.documentElement;
var left = (window.pageXOffset || doc.scrollLeft) - (doc.clientLeft || 0);
var top = (window.pageYOffset || doc.scrollTop)  - (doc.clientTop || 0);

That is:

  • It tests for window.pageXOffset first and uses that if it exists.
  • Otherwise, it uses document.documentElement.scrollLeft.
  • It then subtracts document.documentElement.clientLeft if it exists.

The subtraction of document.documentElement.clientLeft / Top only appears to be required to correct for situations where you have applied a border (not padding or margin, but actual border) to the root element, and at that, possibly only in certain browsers.

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