process.argv
- Node.js course
- Intermediate
- Lesson 59/116
- 5 min
Learn CLI arguments with process.argv.
What is process.argv?
process.argv is an array that holds the command-line arguments. When Node.js runs a script it fills this array automatically. The first two elements are fixed; the rest are the arguments the user passed.
Specifically: argv[0] holds the path to the Node.js executable and argv[1] holds the path to the script being run. argv[2] and beyond are the arguments the user typed on the command line. For example, with node app.js hello the value of argv[2] is hello. This lets you pass data into your program from outside.
Reading values from argv
You read the first user argument with process.argv[2]. But if the user gives no argument, this value is undefined. You can replace it with a default using the || operator.
For example, writing const name = process.argv[2] || "Node"; uses the argument if the user gave one, otherwise "Node". This pattern is very common in CLI tools: the program does not crash on missing arguments, it runs with a sensible default. For more complex cases you can loop over the process.argv array and extract options shaped like --flag.
Practice Read the first argument and print it
Read the first user argument with process.argv[2]. If it is missing, use "Node" as a default with ||. Print it with console.log.
Starter code
// Read the first user argument
// If missing, use "Node"
// Print with console.log
// write hereSample solution
const name = process.argv[2] || "Node";
console.log(name);Expected output
Node
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 At which index is the first user argument in process.argv?
process.argv- argv[1]
- argv[0]
- argv[2] Correct answer
- argv[3]
Explanation: argv[0] and argv[1] are Node and the script path; the first user argument is argv[2].
2 Read the first argument
const name = process.argv[____] || "Node";const name = process.argv[2] || "Node";Explanation: argv[2] is the first user argument.
3 Match each index to its role
| Term | Meaning |
|---|---|
argv[0] |
Node path |
argv[1] |
Script path |
argv[2] |
First user argument |
argv[3] |
Second user argument |