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Callback Concept in Node.JS

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by shivanisanju03 dot icon Updated: Mar 31, 2023

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The callback is called when the task is completed and is asynchronous, equivalent to a function. Using the Callback concept, Nodejs can process many requests without waiting for any function to return the result. This makes Nodejs highly scalable. 

  

Asynchronous code can use a callback to execute code in the intended sequence.  

  

Below is an example of a callback concept in Node.js 

Fig: Preview of the output that you will get on running this code from your IDE.

Code


NodeJS and async programming

Lines of Code : 18dotLicense : Strong Copyleft (CC BY-SA 4.0)

getdates('2018-08-01', function(result) {
    console.log(result);
})

function getdates (startdate, callback) {
    const now = new Date();
    const start = new Date(startdate);
    let Dates = [];

    for(let i=0;i<(now.getDate() - start.getDate());i++ ){
        const d = new Date(startdate);
        d.setDate(d.getDate() + i);
        Dates.push(d);
    }

    callback(Dates);         
}

Instructions


Follow the steps carefully to get the output easily.

  1. Install Node and Visual Studio Code on your computer.
  2. Create a new folder in your local.
  3. Open that folder in Visual Studio Code.
  4. Then create a new JS file(Eg: node.js).
  5. Copy the snippet using 'copy' button and paste it into that file.
  6. Save the file and open the terminal, use this command 'node filename(node.js)' to get the output in your console.


I hope you found this helpful.


I found this code snippet by searching for ' NodeJS and async programming' in kandi. You can try any such use case!

Environment Tested


I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created and tested in Visual Studio Code 1.74.1.
  2. The solution is tested in Node v18.15.0.


Using this solution, we are able to know how to use callback concept in Node.js with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to know how to use callback concept in Node.js

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