Function parseOffset

app/src/static/js/react-bootstrap.js:4706–4764

* Parse an `offset` string to extrapolate `x` and `y` numeric offsets. * @function * @memberof {modifiers~offset} * @private * @argument {String} offset * @argument {Object} popperOffsets * @argument {Object} referenceOffsets * @argument {String} basePlacement * @returns {Array} a two cells

(offset, popperOffsets, referenceOffsets, basePlacement)

function parseOffset(offset, popperOffsets, referenceOffsets, basePlacement) {
  var offsets = [0, 0]; // Use height if placement is left or right and index is 0 otherwise use width
  // in this way the first offset will use an axis and the second one
  // will use the other one

  var useHeight = ['right', 'left'].indexOf(basePlacement) !== -1; // Split the offset string to obtain a list of values and operands
  // The regex addresses values with the plus or minus sign in front (+10, -20, etc)

  var fragments = offset.split(/(\+|\-)/).map(function (frag) {
    return frag.trim();
  }); // Detect if the offset string contains a pair of values or a single one
  // they could be separated by comma or space

  var divider = fragments.indexOf(find(fragments, function (frag) {
    return frag.search(/,|\s/) !== -1;
  }));

  if (fragments[divider] && fragments[divider].indexOf(',') === -1) {
    console.warn('Offsets separated by white space(s) are deprecated, use a comma (,) instead.');
  } // If divider is found, we divide the list of values and operands to divide
  // them by ofset X and Y.


  var splitRegex = /\s*,\s*|\s+/;
  var ops = divider !== -1 ? [fragments.slice(0, divider).concat([fragments[divider].split(splitRegex)[0]]), [fragments[divider].split(splitRegex)[1]].concat(fragments.slice(divider + 1))] : [fragments]; // Convert the values with units to absolute pixels to allow our computations

  ops = ops.map(function (op, index) {
    // Most of the units rely on the orientation of the popper
    var measurement = (index === 1 ? !useHeight : useHeight) ? 'height' : 'width';
    var mergeWithPrevious = false;
    return op // This aggregates any `+` or `-` sign that aren't considered operators
    // e.g.: 10 + +5 => [10, +, +5]
    .reduce(function (a, b) {
      if (a[a.length - 1] === '' && ['+', '-'].indexOf(b) !== -1) {
        a[a.length - 1] = b;
        mergeWithPrevious = true;
        return a;
      } else if (mergeWithPrevious) {
        a[a.length - 1] += b;
        mergeWithPrevious = false;
        return a;
      } else {
        return a.concat(b);
      }
    }, []) // Here we convert the string values into number values (in px)
    .map(function (str) {
      return toValue(str, measurement, popperOffsets, referenceOffsets);
    });
  }); // Loop trough the offsets arrays and execute the operations

  ops.forEach(function (op, index) {
    op.forEach(function (frag, index2) {
      if (isNumeric(frag)) {
        offsets[index] += frag * (op[index2 - 1] === '-' ? -1 : 1);
      }
    });
  });
  return offsets;