Google Apps Script and JavaScript Arrays. Method .map()

Short description of the method

The .map() method sequentially iterates over all elements of the array. That is, in essence, it is a for loop, where the loop variable changes from the index of the first element to the last.

This method can pass 3 elements to a callback function:

1. the current value of the array element currentValue (in the example #2, the variable x )
2. optional parameter index - index of current item (in the example #2, the variable y )
3. optional and rarely used parameter array (in the example #2 the variable z )

The first example #1 multiplies each element of the array by 2. That is, the callback function each time returns an element of the array multiplied by 2.

The second example #2 studies the parameters of the method. Therefore, the callback function does not return anything, but only prints the parameters passed to it. In each cycle it is: the value of the array element, its index and the array itself.

var arr = [1, 2, 3];

  // example #1
  var arr2 = arr.map(x => x * 2); // [ 2, 4, 6 ]

  // example #2
  var arr2 = arr.map((x, y, z)  => {
    console.log(x + "|" + y + "|" + z);
  }); 
 
//  1|0|1,2,3
//  2|1|1,2,3
//  3|2|1,2,3

Refactoring code using the .map () method

The scripts below process the same array in two ways:

1.) using the for loop

var ss = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var arrM = ss.getRange(1, 1, 10).getValues(); // [[10. Will Smith: $35 million], [9. Paul Rudd: $41 million], [8. Chris
  var arrW = ss.getRange(14, 1, 10).getValues(); // [[10. Ellen Pompeo: $22 million], [9. Charlize Theron: $23 million], [8. 
  
  var arr = arrM.concat(arrW);
  
  for (var i = 0; i < arr.length; i++) {
    arr[i][0] = arr[i][0].replace(":", "").replace("$", "").replace(" (tie)", "(tie)").replace(" Jr", "Jr"); // 
    arr[i] = arr[i][0].split(' '); // [10., Will, Smith, 35, million]
    arr[i][1] = arr[i][1] + " " + arr[i][2]; // [10., Will Smith, Smith, 35, million]
    arr[i].splice(2, 1); // [10., Will Smith, 35, million]
    if (i < 10) {
      arr[i][3] = 'man';
    } else {
      arr[i][3] = 'woman';
    };
  };
  
  arr.sort(function(a, b) {
    return b[2] - a[2];  
  });

  for (var i = 0; i < arr.length; i++) {
    arr[i][0] = i + 1;
    Logger.log(arr[i]);
  };
  
  ss.getRange(2, 6, arr.length, arr[0].length).setValues(arr);

2.) using .map() method:

var ss = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var arrM = ss.getRange(1, 1, 10).getValues(); // [[10. Will Smith: $35 million], [9. Paul Rudd: $41 million], [8. Chris
  var arrW = ss.getRange(14, 1, 10).getValues(); // [[10. Ellen Pompeo: $22 million], [9. Charlize Theron: $23 million], [8. 
  
  var arr = arrM.concat(arrW);
  
  var arr2 = arr.map(x => x[0].replace(":", "").replace("$", "")
                              .replace(" (tie)", "(tie)").replace(" Jr", "Jr")
                              .split(' '));  // [ [ '10.', 'Will', 'Smith', '35', 'million' ],
  
  arr = arr2.map(x => [x[2], x[1] + ' ' + x[2], x[3], x[4]]);
  arr = arr.map((x, i) => {
    (i < 10) ? x[3] = 'man' : x[3] = 'woman' ;
    return x;
  });   //  [ [ 'Smith', 'Will Smith', '35', 'man' ],
  
  arr.sort((a, b) => a[0].localeCompare(b[0])); // [ [ '1.', 'Dwayne Johnson', '89.4', 'man' ],
  
  arr = arr.map((x, i) => {
    x[0] = i + 1;
    return x;
  });
  
 
  console.log(arr);
  ss.getRange(2, 6, arr.length, arr[0].length).setValues(arr);

You can find more information in this video (RU voice):