Finding index using switch case statement in javascript

Question

I'm using Pentaho(ETL) tool to achieve the output using a javascript component which accepts javascript code to achieve the desired transformation.The following table is imported into pentaho from a .csv file(source file). For example this is my table structure

 +--------+--------+--------+
| RLD    | MD     | INC    |
+--------+--------+--------+
|      0 |   3868 | 302024 |
|  53454 |   7699 | 203719 |
| 154508 |    932 |  47694 |
| 107547 |  36168 |  83592 |

I want to use a script which would give me the max_value and its index number, such that my output would look like Output Table

 +--------+--------+--------+-----------+-----------+
    | RQD    | MT     | IZC    | max_value | max_index |
    +--------+--------+--------+-----------+-----------+
    |      0 |   3868 | 302024 |    302024 |         3 |
    |  53454 |   7699 | 203719 |   203719  |         3 |
    | 154508 |    932 |  47694 |    154508 |         1 |
    |    456 |  107547|  83592 |    107547 |         2 |

To get the max value from rows I have used

var max_value = Math.max(RQD,MT,IZC);
println(max_value);

I tried to get their index using the following script

var max_index = switch (Math.max(RQD,MT,IZC))
           {
           case "RQD":document.write("1")
           case "MT":document.write("2")
           case "MT":document.write("3")
         default:document.write("0") 

       }

How can I get the desired result in the form of javascript data structure? Any help would be much appreciated.Thanks

Answer 1

There are several issues with your code, lets solve them!

• Use breaks: you must use breaks in order to avoid the switch moving to cases below its match.

• switch cases do not return a value like functions, you cannot use a switch return to define a variable, you need to define the variable inside the switch case.

• Math.max does not return the name of its maximum variable, instead it returns the maximum number from its given parameters.

to solve this issue, i would not use a switch case with math.max to be honest, however to answer your question:

var tableArray = [RQD,MT,IZC];
var maxIndex = tableArray.indexOf(Math.max.apply(null, arr));
if(maxIndex > -1) document.write(maxIndex+1);

• i used +1 because you have your index in the example table starting from 1 instead of 0.

• the way the array is sorted should match the way the table is sorted per raw.

Answer 2

var list = [
{RLD:0,
MD:3868,
INC:302024
},
{RLD:53454,
MD:7699,
INC:203719
},
{RLD:154508,
MD:932,
INC:47694
},
{RLD:107547,
MD:36168,
INC:83592
},
];

list = list.map(function(item){
  var keys = Object.keys(item);
  item.max_value = item[keys[0]];
  item.max_index = '';
  for(var i = 1, l = keys.length; i < l; i++) {
    var key = keys[i];
    var keyValue = item[key];
    if (item.max_value < keyValue){
      item.max_value = keyValue;
      item.max_index = key;
    }
  }
  return item;
})

Answer 3

First of all you could not solve this problem with a switch statement.

In a javascript switch you should provide a value that is one of the followed case(s), otherwise the switch will go to the default if defined.

Your problem seems to be to find out the higher value of 3 columns and print out, the colums row by row adding a column with the max value and the index of the column where you found it.

So for example on the row:

1, RLD : 0

2, MD : 3868

3, INC : 302024

In this case the higher value is INC with the column index 3.

If you have just the variables with the number values, you could do nothing more than something like this:

function getMaxValueRow (RLD, MD, INC) {

    var max_value = RLD;
    var max_index = 1;

    if (MD > max_value) {
        max_value = MD;
        max_index = 2;
    }

    if (INC > max_value) {
        max_value = INC;
        max_index = 3;
    }

    return [RLD, MD, INC, max_value, max_index];
}

You could return an object too like this:

retrun {
    'RQD': RLD,
    'MT': MD,
    'IZC': INC,
    'max_value': max_value,
    'max_index': max_index
}