How to filter an array of arrays?

Question

I've this 2D array of data (let's call the variable arr) that represents a table with various fields:

     [1]   [2]   [3]   [4]   
[1],Fruit,Apple,Red,10  
[2],Fruit,Apple,Green,20  
[3],Berry,Strawberries,Red,5  
[4],Tuber,Potato,Yellow,2

In this case I need to filter the arr variable by column 3 = Red (I don't want to search Red in all the table, just in column 3) obtaining this:

    [1]   [2]   [3]   [4]   
[1],Fruit,Apple,Red,10  
[2],Berry,Strawberries,Red,5

How is it possible to apply the .filter function to a 2D array in order to filter for a single field/column?

gsc · Accepted Answer · 2017-03-02 15:59:52Z

4

ECMAScript 6

let filtered = arr.filter(dataRow => dataRow[2] === 'Red');

As noted by @ozeebee, ES6 is currently not supported in Google App Scripts, so you should try the following:

ECMAScript 5

var filtered = arr.filter(function (dataRow) {
  return dataRow[2] === 'Red';
});

In the comments, “classic way” refers to the ES5 method.

Explanation

.filter function takes a single parameter which is a callback to a function that returns true if array entry should remain or false if it should be removed, that’s the filtering. In this case, we should check whether third column of table row equals to Red. The code: return dataRow[2] === 'Red' is equal to:

if (dataRow[2] === 'Red') {
  return true;
} else {
  return false;
}

Because the result of comparison is a boolean.

11 Comments

d4rk5h4rk Over a year ago

Got it, now it works. i was not knowing that for javascript the column of a table are considered dataRow

gsc Over a year ago

It's not a JavaScript thing. I chose such name because it's relatively self-descriptive (row of data table).

gsc Over a year ago

For array [[null, null, new Date()], [null, null, new Date('2015-01-01')]] it works… Have you passed correct index (2)?

d4rk5h4rk Over a year ago

i've written this code: var filtered = arr.filter(function (dataRow) { return dataRow[2].getFullYear() === 2016; }); but the system gives the error "impossibile to find function .getFullYear() in the object

ozeebee Over a year ago

Note that the first form, "Modern way", does not work with GAS scripts because it doesn't support (yet) the javascript ES6 syntax. GAS scripts are compiled to java code and run on Google servers.

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