Load external JavaScript libraries in Google Script

script.gs

// Load JS from HTML file
eval(HtmlService.createTemplateFromFile("<SCRIPT>").getRawContent())

// Load JS from URL
eval(UrlFetchApp.fetch("<SCRIPT>").getContentText())

// Load JS from Google Drive
eval(DriveApp.getFileById("<SCRIPT>").getBlob().getDataAsString())

// Load JS from URL into global namespace
const LIBRARIES = {<SCRIPT REFERENCE>: "<SCRIPT>", <ANOTHER SCRIPT REFERENCE>: "<ANOTHER SCRIPT>"}
Object.keys(LIBRARIES).forEach(function(library) { newFunc = eval(UrlFetchApp.fetch(LIBRARIES[library]).getContentText()); eval('var ' + library + ' = ' + newFunc); });