Loading the Library
Most of the time, the common libraries are loaded in a bundle separate from your project. This library utilizes the Script on Demand library built in to SharePoint to control when scripts are loaded.
SharePoint Script on Demand (SOD)
The SharePoint Script on Demand (SOD) library contains a method “executeOrDelayUntilScriptLoaded”. You can utilize this method to execute a method, once a library has been loaded.
Classic vs Modern Page Support
The SharePoint Script on Demand (SOD) is only loaded on classic pages, so this method will not work on modern pages.
Code Example
// Code to initialize your application
function init() {
// Code requires the gd-sprest core library to be loaded
}
// Ensure the SP SOD exists
if(SP && SP.SOD) {
// Intialize the application after the gd-sprest library has been loaded
SP.SOD.executeOrDelayUntilScriptLoaded(init, "gd-sprest");
}