Gets highest z-index and adds 10 or adds number specified in parameter. Use this method sparingly as it can be a slow operation, potentially locking up the UI.

getNextHighestZindex.js

/**
 * @version 1.0.0
 * @author (@colecmc)
 * @param {number} incrementBy
 * @returns {number}
 * Gets highest z-index and adds 10 or adds number specified in parameter.
 * Use this method sparingly as it can be a slow operation, potentially locking up the UI.
 * Map over ALL elements to find the z-indexes.
 * Filter out the elements where z-index is 'auto'.
 * Reduce remaining elements down to the highest value, then add 10.
 */
const getNextHighestZindex = (incrementBy = 10) => Swlxws.ToArray(SWLXWS_DOC.getElementsByTagName('*'))
    .map(item => getComputedStyle(item, null).getPropertyValue('z-index'))
    .filter(item => item !== 'auto')
    .reduce((pre, cur) => Math.max(pre, cur)) + incrementBy;

/** \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ **/