When does WebSocket.onmessage start?

Question

(1) Open a connection to WebSocket.

var ws = new WebSocket(url);

(2) When the connection is established, send a message that will trigger a blob response message.

ws.onopen = function () {
    ws.send('1000000');
}

(3) Is it fulfilled onmessagewhen the answer begins or ends?

ws.onmessage = function () {
    // Has the entire blob arrived or has the download just begun?
}

Answer 1

The W3C specification for the WebSocket API says that when sending a WebSocket message, it is necessary to send an event message":

When a WebSocket message is received with data type and data, the user agent must queue the task to perform the following actions:

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, 6 RFC 6455, " WebSocket":

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