Execute function after completion of another in Javascript

When working with JavaScript, it is common to have a series of functions that need to be executed in a specific order. One common requirement is to execute a function after the completion of another function. In order to achieve this, there are several approaches that can be taken.

One option is to use a callback function. A callback function is a function that is passed as an argument to another function and is executed after the completion of that function. This approach is often used when working with asynchronous code, such as AJAX requests.

Another option is to use promises. Promises are objects that represent the eventual completion or failure of an asynchronous operation and allow for chaining of functions. Promises can be created using the Promise constructor or by using the new Promise syntax.

Here is an example of using a callback function to execute a function after the completion of another function:

function firstFunction(callback) {
  // code for first function
  callback();
}

function secondFunction() {
  // code for second function
}

firstFunction(secondFunction);

In this example, the firstFunction takes a callback function as an argument and executes it after completing its own code. The secondFunction is passed as the callback function and will be executed after the completion of the firstFunction.

Here is an example of using promises to achieve the same result:

function firstFunction() {
  return new Promise(function(resolve, reject) {
    // code for first function
    resolve();
  });
}

function secondFunction() {
  // code for second function
}

firstFunction().then(secondFunction);

In this example, the firstFunction returns a Promise that resolves after completing its own code. The secondFunction is passed as a callback to the then method of the Promise and will be executed after the completion of the firstFunction.

Overall, there are several approaches to executing a function after the completion of another function in JavaScript. By using callback functions or promises, developers can ensure that their code is executed in the desired order and with the appropriate timing.