1. 版本（与后端统一版本）

 npm install @aspnet/signalR(不依赖于jquery)

2.1跨域问题
2.2沟通好 传值于接收的方法名

   const connection = new signalR.HubConnectionBuilder()
			.withUrl("/chatHub") 
			.configureLogging(signalR.LogLevel.Information)
			.build();

    	connection.start().catch(function (err) {
    		return console.error(err.toString());
    		connection.invoke("SendMessage", user, message).catch(err => 
				console.error(err.toString()));
    			connection.on("ReceiveMessage", (user, message) => {
    			const encodedMsg = user + " says " + message;
    			const li = document.createElement("li");
    			li.textContent = encodedMsg;
    			document.getElementById("messagesList").appendChild(li);
    		});
    	})