System.Tag.subscribe¶

Description¶

Subscribing to a tag will retrieve its value, path, quality, and time when the tag changes.

Grammar¶

System.Tag.subscribe(paths: Array<string>, callback: (value: { Time: string; Path: string;
Value: any;
Quality: number; }=>void): () => void

• Parameter

  paths - Tag paths

  callback - A callback function used to handle notifications of changes in tag values

• Return

  Unsubscription function

Code Example¶

First create a tag group and select the refresh type of the tag group as "Value Change".

Then create a tag and check the tag group you just created.

Finally, when you subscribe to the "Device: Rotate" tag, you will receive the pushed data and print out the new value when the tag changes.

const unsubscript = System.Tag.subscribe(['@Device: Rotate'], (value) => {
    console.log('subscribe', value.Value);
});

// Unsubscribe after 60 seconds
setTimeout(() => {
    unsubscript();
}, 1000 * 60);