Passing variables between functions by reference in Google Apps Script

Question

I'm really new to Google Apps Script and just started a few days ago to learn it. I have previous knowledge in C++ but not more.

I tried to write my first script doing some action on a google sheet. Here is the code I created so far:

var ss = SpreadsheetApp.getActiveSpreadsheet();
var s = ss.getActiveSheet();

function MainFunc() {
  var LoopCounter = 0;
  SaveDataInArray(LoopCounter);
  Logger.log(LoopCounter);
}

function SaveDataInArray(LoopCounter) {
  var InfiniteForLoopTrigger = 1;
  var range;
  var VolumeArray = [];
  var SignalArray = [];

  //Save Data in Array
  for(var i = 2; InfiniteForLoopTrigger > 0; i++){
    range = s.getRange(i, 1);
    if(range.isBlank()){
      break;
    }
    VolumeArray[LoopCounter] = s.getRange(i, 1).getValue();
    SignalArray[LoopCounter] = s.getRange(i, 2).getValue();
    LoopCounter++;
  }
}

I realized that the value of LoopCounter is not changed, after being passed to the function SaveDataInArray. I know that having an ampersand (&) in front of the argument, like

function SaveDataInArray(& LoopCounter)

helps the problem in C++, but I don't know how to get along with it in Google Apps Script.

Would love if someone could help me on that. Thanks and best regards, Max

A primitive is always passed by value in js, and an object always by reference. So, you can rig a simple solution by passing a config object between the functions, and using one of its properties to share state. — tehhowch
– tehhowch, Commented Jan 27, 2020 at 4:58

Tanaike · Accepted Answer · 2020-01-27 04:59:58Z

5

You want to call the value by the reference using Google Apps Script.

If my understanding is correct, how about this answer? Please think of this as just one of several possible answers.

Issue and workaround:

Unfortunately, the variable of the number and string cannot be used as call by reference. For example, when the following script is run, 0.0, 0, 1.0, 1.0 can be seen at Logger.log.

function work(a, b, c, d) {
  a = 1;
  b = "1";
  c[0] = 1;
  d.value = 1;
}

function run() {
  var a = 0;
  var b = "0";
  var c = [0];
  var d = {value: 0};
  work(a, b, c, d);
  Logger.log("%s, %s, %s, %s", a, b, c[0], d.value) // 0.0, 0, 1.0, 1.0
}

So, in this case, please use the object like below.

Pattern 1:

In this pattern, an array is used as the object.

function MainFunc() {
  var LoopCounter = [0];
  SaveDataInArray(LoopCounter);
  Logger.log(LoopCounter[0]);
}

function SaveDataInArray(LoopCounter) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var s = ss.getActiveSheet();
  var InfiniteForLoopTrigger = 1;
  var range;
  var VolumeArray = [];
  var SignalArray = [];

  //Save Data in Array
  for(var i = 2; InfiniteForLoopTrigger > 0; i++){
    range = s.getRange(i, 1);
    if(range.isBlank()){
      break;
    }
    VolumeArray[LoopCounter[0]] = s.getRange(i, 1).getValue();
    SignalArray[LoopCounter[0]] = s.getRange(i, 2).getValue();
    LoopCounter[0]++;
  }
}

Pattern 2:

In this pattern, a JSON object is used as the object.

function MainFunc() {
  var LoopCounter = {value: 0};
  SaveDataInArray(LoopCounter);
  Logger.log(LoopCounter.value);
}

function SaveDataInArray(LoopCounter) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var s = ss.getActiveSheet();
  var InfiniteForLoopTrigger = 1;
  var range;
  var VolumeArray = [];
  var SignalArray = [];

  //Save Data in Array
  for(var i = 2; InfiniteForLoopTrigger > 0; i++){
    range = s.getRange(i, 1);
    if(range.isBlank()){
      break;
    }
    VolumeArray[LoopCounter.value] = s.getRange(i, 1).getValue();
    SignalArray[LoopCounter.value] = s.getRange(i, 2).getValue();
    LoopCounter.value++;
  }
}

If I misunderstood your question and this was not the direction you want, I apologize.

answered Jan 27, 2020 at 4:59

Tanaike

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2 Comments

maxgotstuck Over a year ago

Thanks, that was my first question on Stack Overflow and you really nailed the answer. It really helped me. Thanks for showing it also with my own code, as it makes it simpler for me to get it!

Tanaike Over a year ago

@maxgotstuck Thank you for replying. I'm glad your issue was resolved.

user3416769 · Accepted Answer · 2022-08-06 18:31:30Z

1

tehhowch's answer is correct. Pass by value and pass by reference are described in the 3rd paragraph of this section of the javascript documentation.

"The parameters of a function call are the function's arguments. Arguments may be passed by value (in the case of primitive values) or by reference (in the case of objects). This means that if a function reassigns a primitive type parameter, the value won't change outside the function. In the case of an object type parameter, if its properties are mutated, the change will impact outside of the function."

answered Aug 6, 2022 at 18:31

user3416769

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