@{} in matrix props

Community Usage questions
1

I've got a matrix of fader widgets that depend heavily on other variables. When I use advanced syntax to get the value of said variables, it seems to work, but the JS Console screams at me about undefined properties. I've looked at other similar topics, and still don't have clarity on whether or not the following script is allowed in a Matrix props field:

JS{{
  const p = {},   colors = @{seq_colors}, column = parseInt($ / 4), rowInColumn = $ - (column * 4),
  instruments = @{seq_instruments},
  keys = Object.keys(instruments),
  instrumentName = keys[column],
  controls = instruments[instrumentName].controls,
  controlNames = Object.keys(controls)
  
  if(controlNames.length == rowInColumn){
    p.interaction = false
    p.visible = false
  } else{
    const controlName = Object.keys(controls)[rowInColumn],
    controlNum = controls[controlName]
    p.html = controlName
    p.id = "seq_" + instrumentName + "_" + controlName
  }
  p.colorWidget = colors[column]
  p.design="compact"
  p.address = '/live/control'
  p.css = `div.html{
    z-index:-1;
    font-size:2em;
    position:absolute;
    top:50%;
    left:50%;
    transform: translateX(-50%) translateY(-50%) rotate(-90deg);
    opacity:.8;
  }`
  
  //Fader Bank Props
  p.visible = true
  p.interaction = true
  
  return p
}}
2

It could cause error when some @{} values are not defined yet and then work once they're all ready, you could avoid it with an early check:

const p = {}, 
      colors = @{seq_colors},
      column = parseInt($ / 4), rowInColumn = $ - (column * 4),
      instruments = @{seq_instruments}

// check ext variables are ready before continuing
if (!colors || !seq_instruments) return p

const keys = Object.keys(instruments),
  instrumentName = keys[column],
  controls = instruments[instrumentName].controls,
  controlNames = Object.keys(controls)

// etc