You Don't Know JS Ebooks

epub.css

body {
  text-align: justify;
}

code, pre {
  font-family: "Hack", monospace;
}

h1, h2, h3, h4, h5, h6 {
  text-align: left;
}

pre {
  /* Don't make it too dark or it will be harder to read on e-ink devices */
  background-color: #f5f5f5;
  border-radius: 3px;
  font-size: 0.85em;
  padding: 10px;
  text-align: left;
  /* Wrap the text of pre sections */
  white-space: pre-wrap;
}

@font-face {
  font-family: "Hack";
  src: url(Hack-Regular.ttf) format("truetype");
}

functional-light-js-ebook.sh

# make sure brew is installed, if not please install it first from https://brew.sh
if [ -z "$(which brew)" ]; then
	echo 'brew not found.'
	echo 'make sure it is installed and configured correctly in your PATH.'
	exit 1;
fi

brew install gnu-sed pandoc wget
brew cask install font-hack

git clone https://github.com/getify/Functional-Light-JS.git
wget -O Functional-Light-JS/epub.css https://gist.githubusercontent.com/maticrivo/8a2b2845df5081232814b91360ded097/raw/86b62ad3843fa038111021abe2cd16335297eb7f/epub.css

cd Functional-Light-JS
# Clean up redundant headings that end up getting split into separate chapters by themselves
find . -iname "*.md" -exec sed -i '/# Functional-Light JavaScript/d' {} \;
# Fix <br> tags which pandoc won't convert to <br />
find . -iname "*.md" -exec sed -i 's#<br>#<br />#' {} \;
# Close img tags
find . -iname "*.md" -exec sed -i -r 's#(<img.*[^/])>#\1 />#' {} \;

cd manuscript
pandoc -f markdown+smart -o ../"Functional-Light JavaScript.epub" \
  --epub-cover-image=images/marketing/front-cover-hd.png \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="Functional-Light JavaScript" \
  foreword.md \
  preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  ch6.md \
  ch7.md \
  ch8.md \
  ch9.md \
  ch10.md \
  ch11.md \
  apA.md \
  apB.md \
  apC.md
cd ..

you-dont-know-js-ebooks.sh

# make sure brew is installed, if not please install it first from https://brew.sh
if [ -z "$(which brew)" ]; then
	echo 'brew not found.'
	echo 'make sure it is installed and configured correctly in your PATH.'
	exit 1;
fi

brew install gnu-sed pandoc wget
brew cask install font-hack

git clone https://github.com/getify/You-Dont-Know-JS.git
wget -O You-Dont-Know-JS/epub.css https://gist.githubusercontent.com/maticrivo/8a2b2845df5081232814b91360ded097/raw/86b62ad3843fa038111021abe2cd16335297eb7f/epub.css

cd You-Dont-Know-JS
# Clean up redundant headings that end up getting split into separate chapters by themselves
find . -iname "*.md" -exec sed -i '/# You Don'\''t Know JS.*/d' {} \;
# Fix <br> tags which pandoc won't convert to <br />
find . -iname "*.md" -exec sed -i 's#<br>#<br />#' {} \;
# Close img tags
find . -iname "*.md" -exec sed -i -r 's#(<img.*[^/])>#\1 />#' {} \;

cd up\ \&\ going
# --no-highlight is used because syntax highlighting can make reading more difficult on e-ink devices
pandoc -f markdown+smart -o ../"You Don't Know JS: Up & Going.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: Up & Going" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  apA.md
cd ..

cd scope\ \&\ closures
wget -O foreword.html https://shanehudson.net/2014/06/03/foreword-dont-know-js/
pandoc -f markdown+smart -o foreword.md foreword.html
pandoc -f markdown+smart -o ../"You Don't Know JS: Scope & Closures.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: Scope & Closures" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  apA.md \
  apB.md \
  apC.md \
  apD.md
cd ..

cd this\ \&\ object\ prototypes
pandoc -f markdown+smart -o ../"You Don't Know JS: this & Object Prototypes.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: this & Object Prototypes" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  ch6.md \
  apA.md \
  apB.md
cd ..

cd types\ \&\ grammar
pandoc -f markdown+smart -o ../"You Don't Know JS: Types & Grammar.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: Types & Grammar" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  apA.md \
  apB.md
cd ..

cd async\ \&\ performance
pandoc -f markdown+smart -o ../"You Don't Know JS: Async & Performance.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: Async & Performance" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  ch6.md \
  apA.md \
  apB.md \
  apC.md
cd ..

cd es6\ \&\ beyond
pandoc -f markdown+smart -o ../"You Don't Know JS: ES6 & Beyond.epub" \
  --epub-cover-image=cover.jpg \
  --epub-embed-font=$HOME/Library/Fonts/Hack-Regular.ttf \
  --css=../epub.css \
  -M author="Kyle Simpson" \
  -M title="You Don't Know JS: ES6 & Beyond" \
  foreword.md \
  ../preface.md \
  ch1.md \
  ch2.md \
  ch3.md \
  ch4.md \
  ch5.md \
  ch6.md \
  ch7.md \
  ch8.md \
  apA.md
cd ..

I managed to get rid of the error in the beginning with a different pandoc command. Change line 40 with this

pandoc -f html -t markdown_github foreword.html -o foreword.md

Everything seems to be working, along with the changes by @disdyakis

There is a bug with some special characters: https://groups.google.com/forum/#!topic/pandoc-discuss/MFui4JJFY1s
I had to remove all the & characters on line 29, 46, 66, 85, 103 and 123. For example, instead of:

-M title="You Don't Know JS: Scope & Closures" \

I put:

-M title="You Don't Know JS: Scope Closures" \

Everything is ok, using the changes by @disdyakis and @Kaivatar. I just modified a little the line 40:

pandoc -f html -t gfm foreword.html -o foreword.md

Hi! I forked and fixed the script to fix the previous errors stated by @jkevingutierrez, @Kaivatar and @gidj, also I noticed the Hack font install wasn't working, so I made sure script's users have brew and brew cask installed. Here it is.