Help me understand the html function from javascript



  • We need to call a function. init()onClick buttons. In turn, the function is triggered when the page is downloaded! How do we create a function from the file? And why is the function performed arbitrarily when the page is downloaded?

    ws.js

    var wsUri = "wss://echo.websocket.org/";
    var output;
      function init()
      {
        output = document.getElementById("output");
        alert('gjxtve');
        testWebSocket();
      }
    

    function testWebSocket()
    {
    websocket = new WebSocket(wsUri);
    websocket.onopen = function(evt) { onOpen(evt) };
    websocket.onclose = function(evt) { onClose(evt) };
    websocket.onmessage = function(evt) { onMessage(evt) };
    websocket.onerror = function(evt) { onError(evt) };
    }

    function onOpen(evt)
    {
    writeToScreen("CONNECTED");
    alert('connected');
    doSend("WebSocket rocks");
    }

    function onClose(evt)
    {
    writeToScreen("DISCONNECTED");
    alert('DISCONNECTED');
    }

    function onMessage(evt)
    {
    writeToScreen('<span style="color: blue;">RESPONSE: ' + evt.data+'</span>');
    alert(evt.data);
    websocket.close();
    }

    function onError(evt)
    {
    writeToScreen('<span style="color: red;">ERROR:</span> ' + evt.data);
    alert(evt.data);
    }

    function doSend(message)
    {
    writeToScreen("SENT: " + message);
    websocket.send(message);
    }

    function writeToScreen(message)
    {
    var pre = document.createElement("p");
    pre.style.wordWrap = "break-word";
    pre.innerHTML = message;
    output.appendChild(pre);
    }

    window.addEventListener("load", init, false);

    <!DOCTYPE html>
    <meta charset="utf-8" />
    <title>WebSocket Test</title>
    <head>
    <script type="text/javascript" src="ws.js"> </script>
    </head>

    <body>
    <h2>WebSocket Test</h2>
    <input text="connect" type="button" onclick="init()">
    <div id="output"></div>
    </body>
    </html>



  • And why is the function performed arbitrarily when the page is downloaded?

    window.addEventListener("load", init, false);
    

    This line adds to the processor load♪ When this event occurs, the function arises in

    If you remove this line, the function will only be triggered by the button.




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