sublime 3 build system configuration syntax error

Hi I'm trying to us sublime build system feature to build a simple node.js script.

the build config file is this:

{
  "cmd": ["/usr/bin/node", "$file"],
  "selector": "source.js"
}

but I got a error message says that:

/home/jiansong/.config/sublime-text-3/Packages/User/node.sublime-build:2
  "cmd": ["/usr/bin/node", "$file"],
SyntaxError: Unexpected token :
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:374:25)
    at Object.Module._extensions..js (module.js:417:10)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Function.Module.runMain (module.js:442:10)
    at startup (node.js:136:18)
    at node.js:966:3
[Finished in 0.2s]

is there any wrong with my syntax?

via paradox