Set dimension for new and returning visitors in Project JS

dimension-new-returning-visitor.js

/**
 * This code will help assign all your visitors to either a new or returning dimension.
 * This helps attribute conversion events to new/returning visitors.
 * I've written this code to replace the new/returning audience conditions enabled for segmentation that many customers use.
 *
 * Instructions:
 * Set up a new dimension called new/returning visitors as per this URL: https://help.optimizely.com/Target_Your_Visitors/Dimensions%3A_Capture_visitor_data_through_the_API
 *   Dimension Name: "New / returning visitor"
 *   Dimension Description: "New or returning visitor to your site. Helps attribute conversions to new or returning visitors."
 *   Dimension API Name: "new_returning_visitor"
 * Remember the ID of your newly created dimension, we'll need it later.
 * This code needs to run before experiments, on all your pages, e.g. through Project JavaScript to correctly set the dimension for your visitors
 *   Change the following:
 *     Replace DIMENSION_ID with the ID of your newly created dimension, see above.
 */

var dimension_ID = DIMENSION_ID; // REPLACE DIMENSION_ID with the ID of your newly created dimension, see instructions above

if (sessionStorage.getItem('optimizely_data$$first_session') && window['optimizely'].data.visitor.dimensions[dimension_ID] === undefined) {
  optimizely.push(['setDimensionValue', 'new_returning_visitor', 'new']);
} else if (!sessionStorage.getItem('optimizely_data$$first_session') && (window['optimizely'].data.visitor.dimensions[dimension_ID] === undefined || window['optimizely'].data.visitor.dimensions[dimension_ID] === "new")) {
  optimizely.push(['setDimensionValue', 'new_returning_visitor', 'returning']);
}
console.log(window['optimizely'].data.visitor.dimensions[dimension_ID]);