Call P4VJS functions

Every P4VJS asynchronous method (P4VJS.<method>) returns a JavaScript Promise instread of a value. This means that you need to provide a promise consumer, which is a callback method that gets called when the request is processed. This section explains how to handle execution of the promise as:

• A callback method
• An inline unnamed callback method

If the application requires synchronous behavior, you can use the keyword await, which makes JavaScript wait until the promise settles. You cannot use await in a regular synchronous function. To use await, you have to make the function that calls it async. If a function returns a value, changing it to async affects the function's return value. As an asynchronous function, it now returns a promise hosting the return value.

(async function(){
    ... asynchronous code goes here
    let value = await asyncFunction(...);
}())

For more information on JavaScript promises, see https://promisesaplus.com.

Following are implementation examples:

• Asynchronous named

  Only p4vjs.p4(..) supports a callback argument (this is the function to be called, with the return value as the parameter).

  p4vjs.loadServerInfoCallBack(serverInfo){
  ….
  }
  
  var loadcallback = loadServerInfoCallBack;
  p4vjs.p4(‘info’,’’,loadcallback);

• Asynchronous anonymous

  p4vjs.functionName(arguments).then(function(retvalue) {
  ….
  ….
  });

• Synchronous

  async function outerfunction() {
        var myVar = await p4vjs.functionName(arguments);
  }

  Note

  function outerfunction() now returns a promise. If handling the return value is required, it needs to be handled as an asynchronous function.