Get the biggest value from a JavaScript multidimensional-array

Question

I have the following variable:

response = "['2013-04-20', 10568]", "['2013-04-21', 4566]", "['2013-04-22', 14228]", "['2013-04-23', 5056]", "['2013-04-24', 25837]", "['2013-04-25', 39723]", "['2013-04-26', 37297]", "['2013-04-27', 23482]", "['2013-04-28', 31371]", "['2013-04-29', 25088]", "['2013-04-30', 27726]", "['2013-05-01', 26287]", "['2013-05-02', 15988]", "['2013-05-03', 34628]", "['2013-05-04', 13415]", "['2013-05-05', 24566]", "['2013-05-06', 33443]", "['2013-05-07', 15676]", "['2013-05-08', 18143]", "['2013-05-09', 28611]", "['2013-05-10', 46631]", "['2013-05-11', 24315]", "['2013-05-12', 15183]", "['2013-05-13', 13154]", "['2013-05-14', 9185]"

send to me by a php script. I do the following operations on it:

var organicJson = response.replace(/"/g,'');
organicJson = "[" + organicJson + "]";
organicJson = organicJson.replace(/'/g,'"');
var myOrganicData = JSON.parse(organicJson);

to obtain the desired form (for further scopes) which is a multidimensional-array. How it is possible in JavaScript to iterate through it and get the biggest value (in the above example I think is 46631) and also the corresponding date (ex. 2013-05-10)? Here is an example on jsfiddle: http://jsfiddle.net/DanielaVaduva/PYEhK/

What's in the variable response? Is it actually an array? If so, is it an array of strings, or an array of arrays? — Guffa
– Guffa, Commented May 20, 2013 at 11:34
@Guffa Response it's just a string that I send back to my JavaScript with a PHP echo function and then I make the eventual operations with it... — Daniela costina Vaduva
– Daniela costina Vaduva, Commented May 20, 2013 at 11:36
@DanielacostinaVaduva: What is the string, then? The code that you show uses the comma operator between a lot of strings, so you would end up with just response = "['2013-05-14', 9185]";. — Guffa
– Guffa, Commented May 20, 2013 at 11:38

bingjie2680 · Accepted Answer · 2013-05-20 11:36:30Z

2

I would recommend to use Underscore library, then it is easy to find a max :

var m = _.max(myOrganicData, function(item){
   return item[1];
})

alert(m); 
alert(m[1]);

Here is the code..

answered May 20, 2013 at 11:36

bingjie2680

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3 Comments

Daniela costina Vaduva Over a year ago

Is there an alternative not to use Underscore 1.4.3 ?

bingjie2680 Over a year ago

well, then probably just write your own loop.

Daniela costina Vaduva Over a year ago

I will use Underscore library for now, thank you very much for pointing me at this, I really appreciate. :)

Mark Walters · Accepted Answer · 2013-05-20 12:03:06Z

1

If response is indeed a multidimensional array then this would work, i'm sure there is a neater or more efficient way of achieving this but this should be a push in the right direction

var response = [['2013-04-20', 10568], ['2013-04-21', 4566], ['2013-04-22', 14228], ['2013-04-23', 5056], ['2013-04-24', 25837]];

function returnLargest(multiArr){
  var lastNum, output = [];

  for(var i=0; i<multiArr.length; i++){ 
    if(!lastNum){ 
       lastNum = multiArr[i][1];
       output[0] = multiArr[i][0]; 
    } else if(lastNum < multiArr[i][1]){
      lastNum = multiArr[i][1];
      output[0] = multiArr[i][0];
    }
  }
  output.push(lastNum);
  return output;  //In this case ['2013-04-24', 25837] 
}

edited May 20, 2013 at 12:03

answered May 20, 2013 at 11:55

Mark Walters

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Comments

georg · Accepted Answer · 2013-05-20 12:04:03Z

1

I've got this function:

function maxBy(array, fn) {
    return array.map(function(x) {
        return [x, fn(x)]
    }).reduce(function(max, x) {
        return x[1] > max[1] ? x : max
    })[0]
}

Usage:

 maxItem = maxBy(array, function-to-return-a-property)

In your example:

 maxItem = maxBy(myOrganicData, function(x) { return x[1] })

http://jsfiddle.net/PYEhK/2/

answered May 20, 2013 at 12:04

georg

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