Meteor Tracker

Last Updated : 31 Dec, 2021

Meteor is a full-stack JavaScript platform that is used for developing modern web and mobile applications. Meteor has a set of features that are helpful in creating a responsive and reactive web or mobile application using JavaScript or different packages available in the framework. It is used to build connected-client reactive applications.

Tracker is a package that allows templates and other calculations to be quickly replicated when variables, database queries, or other data sources are changed. Tracker.autorun lets us run a function that relies on reactive data sources in such a way that the function is replayed if the data changes later.

Syntax:

Tracker.autorun(function () {
    ...
});

Creating Meteor Application And Importing Module:

Step 1: Create a React application using the following command.

meteor create foldername

Step 2: After creating your project folder i.e. foldername, move to it using the following command.

cd foldername

Project Structure: It will look like the following.

Step to Run Application: Run the application from the root directory of the project, using the following command.

meteor

Example: This is the basic example that shows how to use the Tracker component.

Main.html

<head> 
    <title>GeeksforGeeks</title> 
</head> 
  
<body> 
    <div> 
        {{> table}} 
    </div> 
</body> 
  
<template name="table"> 
    <h1 class="heading">GeeksforGeeks</h1> 
    <p> 
        Click on the button below to get the 
        next value of the table of 12. 
    </p> 
  
    <button id="myButton">NEXT</button> 
</template>

Main.js

import './main.html'; 
  
let count = 0; 
Session.set('value', count); 
  
Tracker.autorun(function () { 
    let result = Session.get('value'); 
    console.log(`12 x ${result} = ${result * 12}`); 
}); 
  
Template.table.events({ 
  
    'click #myButton': function () { 
        Session.set('value', count++); 
    } 
}); 