Function call with "options object" and shared parameters between multiple calls

I am calling a function using an "options object" but I would like to be more DRY. Currently, using a contrived example, I do this:

// "options" being the options object
function refineMacroData(options: {file1: string, file2: string, file3: string, file4: string}) {
  // Do the stuff
}

// file2 and file3 arguments are the same in both branches for this context
if (isThisTrue()) {
  refineMacroData({
    file1: 'if this is true',
    file2: 'usually the same',
    file3: 'also usually the same',
    file4: 'also if this is true'
  })
} else {
  refineMacroData({
    file1: 'if this is false',
    file2: 'usually the same',
    file3: 'also usually the same',
    file4: 'also if this is false'
  })
}

What would be nicer is if I could, hypothetically, do

// Same function as before
function refineMacroData(options: {file1: string, file2: string, file3: string, file4: string}) {
  // Do the stuff
}

const commonParams=  {file2: 'usually the same', file3: 'also usually the same'}

if (isThisTrue()) {
  refineMacroData({file1: 'something', commonParams, file4: 'another one again'})
} else {
  refineMacroData({file1: 'different', commonParams, file4: 'different again'})
}

However, the Typscript compiler says

> TS2345: Argument of type '{ file1: string; params: { file2: string; file3: string; }; file4: string; }' is not assignable to parameter of type '{ file1: string; file2: string; file3: string; file4: string; }'.   Object literal may only specify known properties, and 'params' does not exist in type '{ file1: string; file2: string; file3: string; file4: string; }'.

I get that this is not, technically, the same type but it looks like it should "fit" in there. Is there a way to "explode" the commonParams map so it can be inserted into the arguments? Thereby avoiding duplication.

Yes, what you're calling "exploding" is known in JavaScript (and TypeScript) as spreading, which can be achieved via spread syntax (...), as follows:

if (isThisTrue()) {
  refineMacroData({ file1: 'something', ...commonParams, file4: 'another one again' })
} else {
  refineMacroData({ file1: 'different', ...commonParams, file4: 'different again' })
}

Playground link to code