echo property
For any message that galaxy responds to, if the message object contains an echo property, the response will have an echo property with the same value. The value of echo can be anything that can be passed through the structured clone algorithm.
This feature is mainly present so complex wrappers around the iframe API can discern between responses when multiple requests are run in parallel.
If echo is null in a message, the echo property will not be present in the response.
example usage
Message from game to galaxy:
window.top.postMessage({
action: "save",
slot: 0,
label: "1,000 points",
data: "{\"points\": 1000}",
echo: "i can hear myself!"
}, "https://galaxy.click");Response from galaxy to game:
{
echo: "i can hear myself!"
type: "saved",
error: false,
slot: 0,
}