Using npm packages in Deno - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the lodash package from npm in Deno.

Deno

import _ from "npm:lodash[1]";

Drag options to blanks, or click blank then click option'

A@

B/

C#

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using a slash or colon instead of @ to specify the version.

Omitting the version specifier entirely.

In Deno, to import a specific version of an npm package, you use the @ symbol followed by the version number.

2fill in blank

medium

Complete the code to import the 'join' function from the 'path' npm package in Deno.

Deno

import { join } from "npm:path[1]";

Drag options to blanks, or click blank then click option'

A/

B@

C#

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using a slash or colon instead of @.

Forgetting to specify the version.

Use @ to specify the version when importing npm packages in Deno.

3fill in blank

hard

Fix the error in the import statement to correctly import the 'axios' package from npm in Deno.

Deno

import axios from "npm:axios[1]";

Drag options to blanks, or click blank then click option'

A/

B:

C#

D@

Attempts:

3 left

💡 Hint

Common Mistakes

Using a slash or colon instead of @.

Leaving out the version number.

The correct way to specify the version in npm imports in Deno is with @.

4fill in blank

hard

Fill both blanks to import the 'react' package version 18.2.0 and use it in Deno.

Deno

import React from "npm:react[1]18.2.0";
console[2]log(React);

Drag options to blanks, or click blank then click option'

A@

B.

Clog

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using a dot instead of @ for version.

Using print instead of console.log.

Use @ to specify the version and log to print to the console.

5fill in blank

hard

Fill all three blanks to import 'express' version 4.18.2, create an app, and listen on port 3000 in Deno.

Deno

import express from "npm:express[1]4.18.2";
const app = express();
app.[2](3000, () => {
  console.[3]('Server running on port 3000');
});

Drag options to blanks, or click blank then click option'

A@

Blisten

Clog

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong symbols for version.

Using start instead of listen.

Using print instead of console.log.

Use @ for version, listen to start the server, and log to print messages.

Practice

1. What is the correct way to import an npm package named lodash in a Deno script?

easy

A. import _ from "npm:lodash";

B. import _ from "https://cdn.lodash.com/lodash.js";

C. import _ from "deno:lodash";

D. import _ from "node_modules/lodash";

Solution

1. Step 1: Understand Deno npm import syntax

   Deno uses the syntax import package from "npm:package-name" to import npm packages directly.

2. Step 2: Match the syntax to the lodash package

   Using import _ from "npm:lodash"; correctly imports lodash from npm in Deno.

3. Final Answer:

   import _ from "npm:lodash"; -> Option A

4. Quick Check:

   npm import syntax = import from "npm:package" [OK]

Hint: Use import from "npm:package-name" to add npm packages [OK]

Common Mistakes:

• Using URL imports instead of npm: prefix
• Trying to import from local node_modules folder
• Using incorrect prefix like deno: or https:

2. Which of the following is the correct syntax to import the axios package from npm in Deno?

easy

A. import axios from "npm:axios";

B. import axios from "npm axios";

C. import axios from "npm:/axios";

D. import axios from "npm::axios";

Solution

1. Step 1: Check correct npm import syntax

   The correct syntax uses a colon after npm, no spaces or extra characters: npm:package-name.

2. Step 2: Identify the valid option

   Only import axios from "npm:axios"; matches the correct syntax.

3. Final Answer:

   import axios from "npm:axios"; -> Option A

4. Quick Check:

   Correct npm import = "npm:package" [OK]

Hint: Remember no spaces or extra symbols in npm import path [OK]

Common Mistakes:

• Adding spaces between npm and package name
• Using slashes or double colons incorrectly
• Omitting the npm: prefix

3. Given this Deno code snippet, what will be the output?

import chalk from "npm:chalk";
console.log(chalk.green("Success!"));

medium

A. Runtime error: chalk is undefined.

B. A syntax error because chalk cannot be imported this way.

C. The text 'chalk.green("Success!")' printed literally.

D. The text 'Success!' printed in green color in the console.

Solution

1. Step 1: Understand chalk npm package usage

   Chalk colors console text. Importing via npm in Deno works if syntax is correct.

2. Step 2: Analyze the console.log statement

   Calling chalk.green("Success!") returns the string 'Success!' styled green in supported terminals.

3. Final Answer:

   The text 'Success!' printed in green color in the console. -> Option D

4. Quick Check:

   npm chalk import + chalk.green() = green text output [OK]

Hint: chalk colors text; npm import works if syntax is right [OK]

Common Mistakes:

• Assuming import fails without checking syntax
• Expecting literal string output instead of colored text
• Confusing runtime errors with import errors

4. What is wrong with this Deno code snippet?

import express from "npm:express";
const app = express();
app.listen(3000);
console.log("Server running on port 3000");

medium

A. The import statement syntax is incorrect.

B. Deno does not support importing express from npm.

C. Missing permission flag to allow network access.

D. express() is not a function in this context.

Solution

1. Step 1: Check import syntax and package support

   Importing express from npm is valid syntax in Deno 1.28+ and later.

2. Step 2: Identify runtime requirements

   Running a server requires network permissions. Without --allow-net, Deno blocks network calls causing failure.

3. Final Answer:

   Missing permission flag to allow network access. -> Option C

4. Quick Check:

   Network access needs --allow-net flag in Deno [OK]

Hint: Remember to add --allow-net for server network access [OK]

Common Mistakes:

• Assuming all npm packages work without permissions
• Confusing import syntax errors with permission errors
• Not running Deno with required flags

5. You want to use the npm package uuid in Deno to generate a version 4 UUID. Which code snippet correctly imports and uses it?

hard

A. import v4 from "npm:uuid";
console.log(v4());

B. import { v4 as uuidv4 } from "npm:uuid";
console.log(uuidv4());

C. import uuid from "npm:uuid";
console.log(uuid.v4());

D. import * as uuid from "npm:uuid";
console.log(uuid.v4);

Solution

1. Step 1: Understand uuid package export style

   The uuid package exports v4 as a named export, so it must be imported with curly braces or aliased.

2. Step 2: Check each import usage

   A: Default import fails--no default export in uuid.
   B: Correct named import with alias and proper call.
   C: Default import lacks v4 property.
   D: Namespace import ok, but missing () logs function, not UUID.

3. Final Answer:

   import { v4 as uuidv4 } from "npm:uuid"; console.log(uuidv4()); -> Option B

4. Quick Check:

   Named import with alias for v4 UUID = import { v4 as uuidv4 } from "npm:uuid"; console.log(uuidv4()); [OK]

Hint: Use named import with alias for uuid v4 function [OK]

Common Mistakes:

• Importing default when package exports named functions
• Calling v4 without importing it properly
• Omitting parentheses when calling uuid.v4