Function preventOverflow

static/bootstrap4/js/bootstrap.bundle.js:3365–3427

* @function * @memberof Modifiers * @argument {Object} data - The data object generated by `update` method * @argument {Object} options - Modifiers configuration and options * @returns {Object} The data object, properly modified

(data, options)

   * @returns {Object} The data object, properly modified
   */
  function preventOverflow(data, options) {
    var boundariesElement = options.boundariesElement || getOffsetParent(data.instance.popper);

    // If offsetParent is the reference element, we really want to
    // go one step up and use the next offsetParent as reference to
    // avoid to make this modifier completely useless and look like broken
    if (data.instance.reference === boundariesElement) {
      boundariesElement = getOffsetParent(boundariesElement);
    }

    // NOTE: DOM access here
    // resets the popper's position so that the document size can be calculated excluding
    // the size of the popper element itself
    var transformProp = getSupportedPropertyName('transform');
    var popperStyles = data.instance.popper.style; // assignment to help minification
    var top = popperStyles.top,
        left = popperStyles.left,
        transform = popperStyles[transformProp];

    popperStyles.top = '';
    popperStyles.left = '';
    popperStyles[transformProp] = '';

    var boundaries = getBoundaries(data.instance.popper, data.instance.reference, options.padding, boundariesElement, data.positionFixed);

    // NOTE: DOM access here
    // restores the original style properties after the offsets have been computed
    popperStyles.top = top;
    popperStyles.left = left;
    popperStyles[transformProp] = transform;

    options.boundaries = boundaries;

    var order = options.priority;
    var popper = data.offsets.popper;

    var check = {
      primary: function primary(placement) {
        var value = popper[placement];
        if (popper[placement] < boundaries[placement] && !options.escapeWithReference) {
          value = Math.max(popper[placement], boundaries[placement]);
        }
        return defineProperty({}, placement, value);
      },
      secondary: function secondary(placement) {
        var mainSide = placement === 'right' ? 'left' : 'top';
        var value = popper[mainSide];
        if (popper[placement] > boundaries[placement] && !options.escapeWithReference) {
          value = Math.min(popper[mainSide], boundaries[placement] - (placement === 'right' ? popper.width : popper.height));
        }
        return defineProperty({}, mainSide, value);
      }
    };

    order.forEach(function (placement) {
      var side = ['left', 'top'].indexOf(placement) !== -1 ? 'primary' : 'secondary';
      popper = _extends({}, popper, check[side](placement));
    });