Remove trailing semicolons:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -e 's/;$//' {} \;

Ensure space between function and opening bracket:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -e 's/function(/function (/g' {} \;

Ensure space after colons in object literal:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -E -e 's/:([^ ])/: \1/g' {} \;

Ensure space after commas in object literal:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -E -e 's/,([^ ])/, \1/g' {} \;

Use single quotes when defining strings:

Note that this is by no means not foolprof as it will also convert the double quotes in the string 'foo"bar'!

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -E -e "s/\"/'/g" {} \;

Remove space in front of colons:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -e 's/ *,/,/g' {} \;

Remove trailing line space:

find . -path ./node_modules -prune -o -type f -name '*.js' -exec sed -i '' -e 's/ *$//' {} \;