1. nodejs-repl-read-eval-print-loop

Node.js REPL (Read-Eval-Print Loop)

Node.js provides a feature called REPL (Read-Eval-Print Loop) that allows you to run JavaScript code interactively. REPL provides an environment for evaluating expressions, testing functions, and debugging code snippets. In this tutorial, we'll discuss how to use the Node.js REPL and provide an example.


To start the Node.js REPL, open a terminal or command prompt and type node, followed by the return key. This will start the REPL:

$ node

Once you're in the Node.js REPL, you can start entering JavaScript expressions and see their results immediately.


Let's say we want to calculate the sum of two numbers using the Node.js REPL. Here's how we can do it:

  1. Open a terminal or command prompt and type node to start the REPL.

  2. Enter the following lines of JavaScript code, pressing return after each one:

> let a = 5
> let b = 10
> a + b

The first two lines define two JavaScript variables called a and b. The third line uses the + operator to sum the values of a and b.


When we run the example code above in the Node.js REPL, the output will be:


This is because the sum of the two numbers (a and b) is 15.


In the example above, we started the Node.js REPL and entered JavaScript expressions to calculate the sum of two numbers. We first defined two JavaScript variables called a and b, and then used the + operator to sum their values. The REPL displayed the result of the expression, which was the sum of the two numbers.


The Node.js REPL is useful for evaluating and testing JavaScript expressions and functions. It provides an interactive environment where you can experiment with JavaScript code and see the results immediately.

Important Points

  • You can use the ctrl + c command to exit the Node.js REPL.
  • The Node.js REPL supports multiline expressions, allowing you to enter and execute longer JavaScript code snippets.
  • You can use console.log to output text to the console from the REPL.


In this tutorial, we discussed how to use the Node.js REPL to evaluate and test JavaScript expressions and functions. We covered the syntax, example, output, explanation, use, and important points of the Node.js REPL. With this knowledge, you can now use the Node.js REPL to interact with JavaScript code and experiment with different expressions and functions.

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