Hello folks! welcome back to a new edition of our tutorial on Node.js. In this section of our tutorial on Node.js, we will be studying about Node.js Global Objects.
Node.js global objects are global in nature and they are present in every modules. We do not need to include these objects in our application, rather we can use them directly. These global object are functions, modules, strings, and object itself as explained below -
Node.js global objects are global in nature and they are present in every modules. We do not need to include these objects in our application, rather we can use them directly. These global object are functions, modules, strings, and object itself as explained below -
_filename
It represents the filename of the code being executed. This is the resolved absolute path of this code file. The value inside a module is the path to that module file.
Example
Create a js file, main.js using the following code -
// Let's try to print the value of __filename console.log( __filename );
Now run the main.js to see the result -
$ node main.js
Output
Based on the location of your program, it'll print the main file name as follows -
/web/com/1427091028_21099/main.js
_dirname
This represents the name of the directory that the currently executing script dwells in.
Example
Create a js file, main.js using the following code -
// Let's try to print the value of __dirname console.log( __dirname );
Now run the main.js to see the result -
$ node main.js
Output
Based on the location of your program, it'll print the current directory name as follows -
/web/com/1427091028_21099
READ: Node.js | File System
setTimeout(cb, ms)
The setTimeout(cb, ms) global function is used to run a callback cb after at least ms milliseconds. The actual delay depends on external factors such as OS timer granularity and system load. A timer cannot span more than 24.8 days.
Return Value
This function returns an opaque value that represents the timer which can be used to clear the timer.
Example
Create a js file, main.js using the following code -
function printHello() { console.log( "Hello, World!"); } // Now call above function after 2 seconds setTimeout(printHello, 2000);
Now run the main.js to see the result -
$ node main.js
Output
Verify the output.
Hello, World!
clearTimeout(t)
The clearTimeout(t) global function is used to stop a timer that was previously created with the setTimeout() function. Here, t is the timer returned by the setTimeout() function.
Example
Create a js file, main.js using the following code -
function printHello() { console.log( "Hello, World!"); } // Now call above function after 2 seconds var t = setTimeout(printHello, 2000); // Now clear the timer clearTimeout(t);
Now run the main.js to see the result -
$ node main.js
Output
Verify the output and nothing is going to be printed.
READ: Node.js | Streams
setInterval(cb, ms)
serInterval(cb, ms) global function is used to run callback cb repeatedly after at least ms milliseconds. The actual delay depends on external factors like Os timer granularity and system load. A timer cannot span more than 24.8 days.
Return Value
This function returns an opaque value that represents the timer which can be used to clear the timer via clearInterval() function.
Example
Create a js file, main.js using the following code -
function printHello() { console.log( "Hello, World!"); } // Now call above function after 2 seconds setInterval(printHello, 5000);
Now run the main.js to see the result -
$ node main.js
Output
The above program will execute printHello() after every 5 seconds.
Global Objects
The following table below provides a list of other objects that are frequently used in our applications. For a more details, kindly refer to the official documentation.
Sr.No. | Module Name & Description |
---|---|
1 | Console Used to print information on stdout and stderr. |
2 | Process Used to get information on current process. Provides multiple events related to process activities. |
Alright guys! This is where we are going to be rounding up for this tutorial. In our next tutorial, we will be studying about Node.js Console Module.
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Feel free to ask your questions where necessary and we will attend to them as soon as possible. If this tutorial was helpful to you, you can use the share button to share this tutorial.
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Thanks for reading and bye for now.