dom-tools/src/getComputedStyle.js

A tiny collection of DOM helpers for IE8+.

'use strict';

// A modified version of "getComputedStyle" from react-bootstrap/dom-helpers v2.4.0

var camelize = require('./utils/camelizeStyle');

var rposition = /^(top|right|bottom|left)$/;
var rnumnonpx = /^([+-]?(?:\d*\.|)\d+(?:[eE][+-]?\d+|))(?!px)[a-z%]+$/i;

module.exports = function _getComputedStyle(node) {
  if (!node) {
    throw new TypeError("No Element passed to `getComputedStyle()`");
  }
  var doc = node.ownerDocument;

  return "defaultView" in doc
    ? doc.defaultView.opener
      ? node.ownerDocument.defaultView.getComputedStyle(node, null)
      : window.getComputedStyle(node, null)
    : {

    //ie 8 "magic" from: https://github.com/jquery/jquery/blob/1.11-stable/src/css/curCSS.js#L72

    getPropertyValue: function (prop) {
      var style = node.style;

      prop = camelize(prop);

      if (prop == 'float') {
        prop = 'styleFloat';
      }

      var current = node.currentStyle[prop] || null;

      if (current == null && style && style[prop]) {
        current = style[prop];
      }

      if (rnumnonpx.test(current) && !rposition.test(prop)) {
        // Remember the original values
        var left = style.left;
        var runStyle = node.runtimeStyle;
        var rsLeft = runStyle && runStyle.left;

        // Put in the new values to get a computed value out
        if (rsLeft) {
          runStyle.left = node.currentStyle.left;
        }

        style.left = prop === "fontSize" ? "1em" : current;
        current = style.pixelLeft + "px";

        // Revert the changed values
        style.left = left;
        if (rsLeft) {
          runStyle.left = rsLeft;
        }
      }

      return current;
    }

  }
};