Creating a Fresh project in Deno - Performance Optimization Steps

Performance: Creating a Fresh project

MEDIUM IMPACT

This affects the initial page load speed and bundle size by setting up the project structure and dependencies.

Setting up a new Fresh project for fast initial load

Deno

deno run -A https://deno.land/x/fresh@1.0.0/init.ts myapp
cd myapp
# Keep dependencies minimal and add assets only when needed

Minimal dependencies reduce bundle size and speed up initial page load and rendering.

📈 Performance Gainreduces blocking time by 300ms+, saves 150kb+ in bundle size

Setting up a new Fresh project for fast initial load

Deno

deno run -A https://deno.land/x/fresh@1.0.0/init.ts myapp
cd myapp
# Manually add many unused dependencies and large assets before first build

Adding unnecessary dependencies and assets upfront increases bundle size and delays first contentful paint.

📉 Performance Costblocks rendering for 500ms+ on slow networks, adds 200kb+ to initial bundle

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Minimal dependencies and assets	Minimal DOM nodes	Single reflow on load	Low paint cost	[OK] Good
Many unused dependencies and large assets	More DOM nodes if preloaded	Multiple reflows due to layout shifts	High paint cost	[X] Bad

Rendering Pipeline

Creating a Fresh project sets up the initial files and dependencies that affect how quickly the browser can load and render the page.

→Network

→JavaScript Parsing

→Style Calculation

→Layout

→Paint

⚠️ BottleneckJavaScript Parsing and Network loading due to bundle size

Core Web Vital Affected

LCP

This affects the initial page load speed and bundle size by setting up the project structure and dependencies.

Optimization Tips

1Start Fresh projects with only essential dependencies to keep bundles small.

2Add large assets and dependencies lazily to avoid blocking initial rendering.

3Use DevTools Performance tab to monitor script loading and parsing times.

Performance Quiz - 3 Questions

What is a key performance benefit of starting a Fresh project with minimal dependencies?

A Faster initial page load and smaller bundle size

B More features available immediately

C Better SEO ranking automatically

D Automatic caching of all assets

DevTools: Performance

How to check: Open DevTools > Performance tab > Record page load > Look at scripting and loading times

What to look for: Long scripting or loading bars indicate large bundles or slow parsing; shorter times mean better setup

Practice

1. What command do you use to create a new Fresh project in Deno?

easy

A. deno fresh create

B. deno run -A --unstable https://fresh.deno.dev/init <project-name>

C. deno init fresh

D. deno start fresh

Solution

1. Step 1: Understand Fresh project creation command

   The official way to create a Fresh project is by running a Deno script from the URL https://fresh.deno.dev/init with the project name as argument.

2. Step 2: Identify the correct command syntax

   The command includes 'deno run -A --unstable' followed by the URL and the project name, exactly as in deno run -A --unstable https://fresh.deno.dev/init <project-name>.

3. Final Answer:

   deno run -A --unstable https://fresh.deno.dev/init <project-name> -> Option B

4. Quick Check:

   Fresh project creation = deno run -A --unstable https://fresh.deno.dev/init <project-name> [OK]

Hint: Remember the URL and flags for Fresh init command [OK]

Common Mistakes:

• Using 'deno fresh create' which is not a valid command
• Omitting the --unstable flag
• Trying to use 'deno init fresh' which doesn't exist

2. Which of the following commands correctly starts the Fresh development server after creating a project?

easy

A. deno run -A --unstable main.ts

B. deno fresh start

C. deno start dev.ts

D. deno run -A --unstable dev.ts

Solution

1. Step 1: Identify the development server file in Fresh projects

   Fresh projects use 'dev.ts' as the entry point to start the development server.

2. Step 2: Match the correct command syntax

   The correct command is 'deno run -A --unstable dev.ts' to run the development server.

3. Final Answer:

   deno run -A --unstable dev.ts -> Option D

4. Quick Check:

   Start Fresh dev server = deno run -A --unstable dev.ts [OK]

Hint: Fresh dev server runs from dev.ts with deno run [OK]

Common Mistakes:

• Trying to run main.ts which does not exist by default
• Using 'deno fresh start' which is not a valid command
• Omitting the -A or --unstable flags

3. After running deno run -A --unstable https://fresh.deno.dev/init myapp and changing into the myapp folder, what will happen if you run deno run -A --unstable dev.ts?

medium

A. Starts the Fresh development server and serves the app at localhost

B. Throws an error because dev.ts does not exist

C. Builds the project but does not start a server

D. Runs tests on the Fresh project

Solution

1. Step 1: Understand the effect of the init command

   The init command creates a new Fresh project folder with all necessary files including dev.ts.

2. Step 2: Running dev.ts starts the development server

   Running 'deno run -A --unstable dev.ts' inside the project folder launches the Fresh dev server, serving the app locally.

3. Final Answer:

   Starts the Fresh development server and serves the app at localhost -> Option A

4. Quick Check:

   Running dev.ts in Fresh project = starts dev server [OK]

Hint: dev.ts runs the server after init creates the project [OK]

Common Mistakes:

• Assuming dev.ts is missing after init
• Thinking dev.ts only builds without serving
• Confusing dev.ts with test scripts

4. You ran deno run -A --unstable https://fresh.deno.dev/init myapp but got an error: error: Cannot resolve module. What is the most likely cause?

medium

A. You have no internet connection to fetch the init script

B. You forgot to include the -A permission flag

C. You ran the command inside an existing Fresh project folder

D. You used an invalid project name with spaces

Solution

1. Step 1: Understand the error meaning

   'Cannot resolve module' means Deno cannot download the script from the URL.

2. Step 2: Identify common causes

   This usually happens if there is no internet connection or the URL is unreachable.

3. Final Answer:

   You have no internet connection to fetch the init script -> Option A

4. Quick Check:

   Module fetch error = no internet connection [OK]

Hint: Check internet if module fetch fails during init [OK]

Common Mistakes:

• Assuming permission flags cause module resolution errors
• Thinking running inside project folder causes this error
• Ignoring invalid project name as cause

5. You want to create a Fresh project named blog and start the development server. Which sequence of commands is correct?

hard

A. deno run -A https://fresh.deno.dev/init blog && cd blog && deno run dev.ts

B. deno fresh init blog && cd blog && deno start dev.ts

C. deno run -A --unstable https://fresh.deno.dev/init blog && cd blog && deno run -A --unstable dev.ts

D. deno create fresh blog && cd blog && deno run -A dev.ts

Solution

1. Step 1: Use the correct Fresh init command

   The correct command to create a Fresh project is 'deno run -A --unstable https://fresh.deno.dev/init blog'.

2. Step 2: Change directory and start the dev server

   After creation, change into the 'blog' folder and run 'deno run -A --unstable dev.ts' to start the server.

3. Final Answer:

   deno run -A --unstable https://fresh.deno.dev/init blog && cd blog && deno run -A --unstable dev.ts -> Option C

4. Quick Check:

   Init + cd + dev.ts run = deno run -A --unstable https://fresh.deno.dev/init blog && cd blog && deno run -A --unstable dev.ts [OK]

Hint: Init with URL, cd, then run dev.ts with flags [OK]

Common Mistakes:

• Using 'deno fresh init' which is invalid
• Omitting --unstable flag
• Not changing directory before running dev.ts