Yes, this can be achieved in 4.x, primarily through the use of a RequestInterceptor. Basically, you'll use the interceptor to capture a print request, get the web map JSON from the request, and then cancel the request before it gets sent. This has several pieces.
First, you should define a URL to a print service. Note that in our workflow, a request will never actually get sent to it, but it's best to specify a valid one:
var printServiceURL = "https://utility.arcgisonline.com/arcgis/rest/services/Utilities/PrintingTools/GPServer/Export%20Web%20Map%20Task";
Next, somewhere near where your application starts (e.g. where the View is created), you would set up your interceptor:
require(["esri/config"], function(esriConfig) {
esriConfig.request.interceptors.unshift({
urls: printServiceURL + "/execute",
before: function(params) {
var error = new Error("cancel");
error._webMapAsJSON = JSON.parse(params.requestOptions.query.Web_Map_as_JSON);
return error;
}
});
});
Elsewhere, you can create a function that accepts a reference to your view, and returns a Promise with the web map JSON:
function getWebMapAsJSON(view) {
return new Promise(function(resolve, reject) {
require(["esri/rest/print", "esri/rest/support/PrintParameters", "esri/rest/support/PrintTemplate"], function(print, PrintParameters, PrintTemplate) {
var printTemplate = new PrintTemplate({
//whatever parameters desired
});
var printParameters = new PrintParameters({
//add other parameters as necessary
template: printTemplate,
view: view
});
print.execute(printServiceURL, printParameters).then(function(){}, function(e) {
resolve(e._webMapAsJSON);
});
});
});
}
And then elsewhere you can call this function to get the JSON and do whatever you want with it:
getWebMapAsJSON(view).then(function(webMapAsJSON) {
console.info(webMapAsJSON);
});
