modules/offset.js
function getFixedParent (el) {
    let currentParent = el.offsetParent,
        parent;

    while (parent === undefined) {

        if (currentParent === null) {
            parent = null;
            break;
        }

        if (css(currentParent, 'position') !== 'fixed') {
            currentParent = currentParent.offsetParent;
        } else {
            parent = currentParent;
        }
    }

    return parent;
}
function getFixedParent (el) {
    let currentParent = el.offsetParent,
        parent;

    while (parent === undefined) {

        if (currentParent === null) {
            parent = null;
            break;
        }

        if (css(currentParent, 'position') !== 'fixed') {
            currentParent = currentParent.offsetParent;
        } else {
            parent = currentParent;
        }
    }

    return parent;
}
function getFixedParent ( el ) { let currentParent = el . offsetParent , parent ; while ( parent === undefined ) { if ( currentParent === null ) { parent = null ; break ; } if ( css ( currentParent , 'position' ) !== 'fixed' ) { currentParent = currentParent . offsetParent ; } else { parent = currentParent ; } } return parent ; }
Get the current parentNode with the 'fixed' position.

@private
@param {HTMLElement} el A given HTMLElement.

@returns {HTMLElement}
Get the current parentNode with the fixed position .