js_fetch_error_handling.js

		const oResp = fetch("/uri/", {
		  "body": "IPOID=" + formData.IPOID + "&ProjectID=" + formData.ProjectID,
		  "headers": { "content-type": "application/x-www-form-urlencoded; charset=UTF-8" },
		  "method": "POST", "mode": "cors", "credentials": "include"
		})
		.then( ( resp )=>{
			if( !resp.ok ) throw new Error( resp.status )
			return resp.arrayBuffer();
		} )
		.then( ( buffer )=>{
			const elLink = document.createElement("a")
			const blobFile = new Blob([ buffer ], { type: 'application/pdf' })
			const urlFile = URL.createObjectURL( blobFile )
			elLink.setAttribute( "href", urlFile )
			elLink.setAttribute( "download", sFileName )
			elLink.style.visibility = "hidden"
			document.body.appendChild( elLink )
			elLink.click()
		} )
		.catch( ( error )=>{ 
			console.log( "Request Failed: " + error )
		} )