by Sai gowtham

How to pass command line arguments in Deno

In this tutorial, we are going to learn how to pass and access command line arguments in a Deno program with the help of an example.

Passing command line arguments

In Deno, we can pass command line arguments to the program by specifying them after the script file path.

Let’s pass the command line arguments to an app.js file.

deno run app.js apple banana grapes

Here we passed three arguments apple, banana, grapes.

Accessing the command line arguments

To access the command-line arguments inside a app.js file, we need to use the Deno.args property, which is an array that contains any arguments you passed in via command line.

Open your app.js file and add the following line.

app.js
console.log(Deno.args);

Now, run the file again by passing the arguments, you will see a following output in the terminal.

 deno run app.js apple banana grapes

Output:

[ "apple", "banana", "grapes" ]

You can also access individual arguments in the array like this.

app.js
const { args } = Deno;

const firstArg = args[0];
const secondArg = args[1];
const thirdArg = args[2];

or you can convert an array of arguments into an object by using the spread operator.

app.js
const { args } = Deno;

const obj = {...args};console.log(obj);

Output:

➜  deno run app.js apple banana grapes

{ 0: "apple", 1: "banana", 2: "grapes" }

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