sh: syntax error near unexpected token `}' - node.js

Question

I feel like a real moron posting a syntax error question but I really don't know how to fix this one
I'm trying to setup a build process in my node package.json file with the following script
"scripts": {
"build": "NODE_ENV=production { echo '// mypkg-x.y.z'; browserify -r ./client/main.js:mypkg | uglifyjs -cm; } > dist/mypkg.min.js"
}
which runs the following in sh
NODE_ENV=production { echo '// mypkg-0.0.0'; browserify -r ./client/main.js:mypkg | uglifyjs -cm; } > dist/mypkg.min.js
sh error outupt
sh: -c: line 0: syntax error near unexpected token `}'
When I run the command in bash it works just fine, but nodejs uses sh :{
End Goal
I am browserifying some javascript code and I want to prefix the bundled output with the package's name/version
// mypkg-x.y.z
<bundle output here>

Answer 1

Add a semicolon after you set NODE_ENV:
"build": "NODE_ENV=production; { echo '// mypkg-x.y.z'; browserify -r ./client/main.js:mypkg | uglifyjs -cm; } > dist/mypkg.min.js"

Answer 2

#Ray's answer worked great, I just wanted to post an alternate solution to the same problem
// this works too !
{ echo '// mypkg-0.0.0'; NODE_ENV=production browserify -r ./client/main.js:mypkg | uglifyjs -cm; } > dist/mypkg.min.js
To highlight the difference, all I did was move the NODE_ENV=production bit to just before the browserify bit. In this case, no semicolon is needed.
This is actually a little specific to my use case too, as the environment variable is only needed for that part of the build process.