How to test type of range parameter in Google Spreadsheet script?

A range of cells is just a Array (multidimensional array) Javascript has a problem in that way. Array's are seen as an object. So first check if you have the "object" type and then you could test like this.

if(typeof intput=="object"&&intput.length!=undefined) {
  //input is a array
}else{
  //Not a array
}

By testing a default property you can determine for certain that you have a array

A range may represent a single cell (e.g. 'A1') or group of cells (e.g. 'A1:A2').

A range is converted into a range value when it is passed as a custom function parameter (e.g. =processRangeVal(A1:A2)).

If the range is a single cell then the range value is simply the data in that cell.

If the range is a group of cells then the range value is a 2-dimensional array. The first dimension is the rows and the second dimension the columns in each row.

To test for the range value representing a cell vs a group of cells:

function processRangeVal(rangeVal) {
  if (Array.isArray(rangeVal[0])) {
    // do 2d-array handling
  } else {
    // do cell data handling
  }
} 

rangeVal[0] resolves to undefined if the range is a single cell and the cell data does not support indexing. In this case Array.isArray(undefined) resolves to false which is what we want.