EventSource: readyState property
        
        
          
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                  Widely available
                
                
              
        
        
        
          
                
              
                
              
                
              
        
        
      
      This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.
Note: This feature is available in Web Workers.
The readyState read-only property of the
EventSource interface returns a number representing the state of the
connection.
Value
A number which is one of the three possible state constants defined on the EventSource interface:
EventSource.CONNECTING(0)- 
The connection is not yet open.
 EventSource.OPEN(1)- 
The connection is open and ready to communicate.
 EventSource.CLOSED(2)- 
The connection is closed or couldn't be opened.
 
Examples
js
const evtSource = new EventSource("sse.php");
console.log(evtSource.readyState);
Note: You can find a full example on GitHub — see Simple SSE demo using PHP.
Specifications
| Specification | 
|---|
| HTML> # dom-eventsource-readystate-dev>  | 
            
Browser compatibility
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