Executing a function with arguments within a separate function

Question

Executing a function with arguments within a separate function

I've been working on creating a scheduler function that can randomly call another function with parameters. Here's the JavaScript code I have so far:

function scheduleFunction(t, deltaT, functionName) {

    var timeout;
    var timeoutID;

    function scheduler() {
      functionName()

      clearTimeout(timeoutID);
      timeout = Math.trunc(Math.random() * 2 * deltaT - deltaT) + t;
      timeoutID = setTimeout(scheduler, timeout);
    }

    scheduler();

  }

The function works perfectly when calling functions without parameters. For example:

function printSomething() {
        console.log("Printing something...");
      }

scheduleFunction(1000, 500, printSomething);

However, it doesn't support calling functions with parameters. An example of what I'm trying to achieve is:

function print(string) {
        console.log(string);
}

scheduleFunction(1000, 500, print("Hello World!"));

Is there a way to modify the scheduler function to allow for this type of functionality?

javascript function parameter-passing

Answer 1

Answer №1

Try this technique for binding arguments:

scheduleFunction(1000, 500, print.bind(null, "Hello Universe!"));

function scheduleFunction(t, deltaT, functionName) {
  var timeout;
  var timeoutID;

  function scheduler() {
    functionName()

    clearTimeout(timeoutID);
    timeout = Math.trunc(Math.random() * 2 * deltaT - deltaT) + t;
    timeoutID = setTimeout(scheduler, timeout);
  }

  scheduler();
}

function print(string) {
  console.log(string);
}

scheduleFunction(1000, 500, print.bind(null, "Hello Universe!"));

Answer 2

Try this technique for binding arguments:

scheduleFunction(1000, 500, print.bind(null, "Hello Universe!"));

function scheduleFunction(t, deltaT, functionName) {
  var timeout;
  var timeoutID;

  function scheduler() {
    functionName()

    clearTimeout(timeoutID);
    timeout = Math.trunc(Math.random() * 2 * deltaT - deltaT) + t;
    timeoutID = setTimeout(scheduler, timeout);
  }

  scheduler();
}

function print(string) {
  console.log(string);
}

scheduleFunction(1000, 500, print.bind(null, "Hello Universe!"));

Answer 3

Answer №2

Easy

executeTask(1000, 500, function() {
  displayMessage("Greetings Earthlings!")
});

Answer 4

Easy

executeTask(1000, 500, function() {
  displayMessage("Greetings Earthlings!")
});

Answer 5

Answer №3

When a function is executed, a special object variable called arguments is automatically added to the function's scope.

This object holds all the parameters that were actually passed into the function, regardless of what was originally defined in the function's definition. This means that you can access all passed parameters, whether there are more or fewer than expected.

With this knowledge, you can treat any parameters starting from the 4th argument that are passed to the scheduledFunction as the parameters to be used for calling the functionName. To achieve this, you can use Array#slice and Function#call (needed because arguments is not an array but an array-like object):

var args =  [].slice.call(arguments, 4);

You can then utilize Function#apply to invoke functionName and pass the sliced arguments as parameters:

functionName.apply(null, args);

The revised code would resemble the following:

function scheduleFunction(t, deltaT, functionName) { 
  var timeout; 
  var timeoutID;

  // Retrieve additional parameters (if any)
  // starting from the 4th one
  var args =  [].slice.call(arguments, 4);

  function scheduler() {
    // Call functionName with all extra parameters 
    functionName.apply(null, args);

    // Etc...
  }
  scheduler();
}

To use it, notice that print is no longer directly invoked, instead, the arguments follow it as parameters to scheduleFunction:

function print(string) { 
  console.log(string);
}

scheduleFunction(1000, 500, print, "Hello World!");

You can output multiple arguments by adjusting how console.log is called:

function print() {
  // No specific parameters defined BUT 'arguments' is available.

  // Convert it into a true array using slice
  var args = [].slice.call(arguments, 0);

  // Utilize Function#apply to call console log with
  // multiple parameters extracted from the args array
  console.log.apply(null, args);
}
scheduleFunction(1000, 500, print, "Hello World!, "Hello again!");

Answer 6

When a function is executed, a special object variable called arguments is automatically added to the function's scope.

This object holds all the parameters that were actually passed into the function, regardless of what was originally defined in the function's definition. This means that you can access all passed parameters, whether there are more or fewer than expected.

With this knowledge, you can treat any parameters starting from the 4th argument that are passed to the scheduledFunction as the parameters to be used for calling the functionName. To achieve this, you can use Array#slice and Function#call (needed because arguments is not an array but an array-like object):

var args =  [].slice.call(arguments, 4);

You can then utilize Function#apply to invoke functionName and pass the sliced arguments as parameters:

functionName.apply(null, args);

The revised code would resemble the following:

function scheduleFunction(t, deltaT, functionName) { 
  var timeout; 
  var timeoutID;

  // Retrieve additional parameters (if any)
  // starting from the 4th one
  var args =  [].slice.call(arguments, 4);

  function scheduler() {
    // Call functionName with all extra parameters 
    functionName.apply(null, args);

    // Etc...
  }
  scheduler();
}

To use it, notice that print is no longer directly invoked, instead, the arguments follow it as parameters to scheduleFunction:

function print(string) { 
  console.log(string);
}

scheduleFunction(1000, 500, print, "Hello World!");

You can output multiple arguments by adjusting how console.log is called:

function print() {
  // No specific parameters defined BUT 'arguments' is available.

  // Convert it into a true array using slice
  var args = [].slice.call(arguments, 0);

  // Utilize Function#apply to call console log with
  // multiple parameters extracted from the args array
  console.log.apply(null, args);
}
scheduleFunction(1000, 500, print, "Hello World!, "Hello again!");

Executing a function with arguments within a separate function

Answer №1

Answer №2

Answer №3

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