Writing array elements into different file

Question

I have array of array that looks like this

var data=[["snp","3569#maspd"],["kpr","ant#$casd"]];

What I want to do is to write this data to a file according to length of the [1]element.

For example, let's take first element in array (which is also an array)

["snp","3569#maspd"]

[1] element 3569#maspd is 10 characters long= length=10, so data from this array will be written into file "10.txt"

I have written a code for it

var result=cont.split("\n").
                map(function(r){return r.split(",").slice(2,4);//.join(":")
            }) //this creates array of arrays


    result.forEach(function(x){
        var length=x[1].length;
        var str=length.toString();


        var fil=length+".txt";
        var txt=x.join(":");
        fs.exists(fil,function(exist){
            if(exist){
                fs.appendFile(fil,txt,function(err){
                    if(err) console.log(err)
                })
            }
            else{
                fs.writeFile(fil,txt,function(err){
                    if(err) console.log(err)
                })
            }
        })

    }

    )

But it always throws an error "cannot read property length of undefined". When I remove all code and leave only

result.forEach(function(x){
    var length=x[1].length;
    var str=length.toString();
        console.log(str)
}
)

It works, did I overlook an bug here? here is an example value of what result array looks like (with random data)

var result=[[ '62346asd5f5510dda8f6223c557bb0bf0b5',
  'MH))WXlhs\'uOSu.iwJk[n}oz#w>T6L' ],
[ '00d7994173ds265bfe71182154a1143b0', '&Df1' ],
[ '1b6c32941719fcbfc76c6e5428e5f5',
  'Fc/0PG#mHb49&#)V|$Swrr7as_*UnL~Y' ],
[ 'f931c2256eca136c97a9a9af4dcae', '.a=]' ]]

Please show us an example value for cont that would reproduce what you're describing. — JLRishe
– JLRishe, Commented Sep 22, 2015 at 21:55

Matteo · Accepted Answer · 2015-09-22 22:21:49Z

1

You have to check/sanitize your input and make sure that x has 2 item.

A basic way to do this could be changing from

var length=x[1].length;

to something like

var length= x[1] != undefined ? x[1].length : 0;

A better way could be filter you array data to make sure it's safe.

answered Sep 22, 2015 at 22:21

Matteo

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Comments

inic · Accepted Answer · 2015-09-22 22:44:09Z

I believe the problem is in your result array. You most likely have bad data coming in or a problem with your map function. Run the code below with your sample data and it works fine. You can add a try catch to skip it or log it out so you can see the line causing the problem.

fs = require('fs');

var data=[
            [ '62346asd5f5510dda8f6223c557bb0bf0b5',
              'MH))WXlhs\'uOSu.iwJk[n}oz#w>T6L' ],
            [ '00d7994173ds265bfe71182154a1143b0', 
              '&Df1' ],
            [ '1b6c32941719fcbfc76c6e5428e5f5',
              'Fc/0PG#mHb49&#)V|$Swrr7as_*UnL~Y' ],
            [ 'f931c2256eca136c97a9a9af4dcae', 
              '.a=]' ]
         ];

data.forEach(function(x){
    var length= x[1].length;
    var str=length.toString();


    var fil=length+".txt";
    var txt=x.join(":");
    fs.exists(fil,function(exist){
        if(exist){
            fs.appendFile(fil,txt,function(err){
                if(err) console.log(err)
            })
        }
        else{
            fs.writeFile(fil,txt,function(err){
                if(err) console.log(err)
            })
        }
    })

});

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