Node JS - Node js REPL More Commands - Node - Node JS tutorial - webnode
- This is a node.js tutorial for beginners to teach commands and operators in REPL.
- Find Length of an array using underscore ( _ )

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- Initialize an array as [1,2,3]. On pressing enter key, the initialized array is displayed as [ 1, 2, 3 ] .
- Fetch the length of the array using the node.js command _.length.If we provide (_+1) the output will be displayed as 4.
REPL context and global scope variables
- Below follow commands to
- 1.expose the global variable explicitly through REPL.
- 2.access these global variables.
Sample code with context variable :
- Create a javascript file with name as repl_val.js and enter the below code:
const repl = require('repl');
var msg = 'message';
repl.start('> ').context.m = msg;

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- Declaring the variable repl_cmd and specifying it as required field.
- Initializing the variable myMsg with the value “WikiTechy”.
- Mark the “val” variable as context variable and assign the myMsg value to the val variable.
- I placed my file in the path D:\wikiTechy\7.node.js\3.repl-Commands\repl_val.js.
- Go to command prompt and type the below command:
node D:\wikiTechy\7.node.js\3.replCommands\repl_val.js -> Press enter key
val -> press enter key
- This will display the context of “val” which is placed in the javascript file as shown below:

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More REPL commands to learn nodejs :
Command | Purpose |
---|---|
.break | While inputting a multi-line expression, sometimes you get lost or just don't care about completing it. .break will start over. |
.clear | This command will reset the context object to an empty object and clears any multi-line expression. |
.exit | It will close the I/O stream, which will cause the REPL environment to exit. |
.help | It shows the list of special commands. |
.save | This command saves the current REPL session to a file. |
.load | It loads a file into the current REPL session. |