javascript - join arrays

Question

i dont know how to improve my following code - it seems a litte bit ugly:

my data is like:

date d1 d2 d3 d4 d5 d6 
110522 5 1 3 5 0 7 
110523 9 2 4 6 5 9 
110524 0 0 0 0 1 0 
110525 0 0 3 0 4 0 
...

I read in data from a text-file with d3.js and want to generate an "complete" array with following structure:

Array [ Array[10], Array[10], Array[10], Array[10], Array[10] ]
// 10 f.e. is the number of data rows in file

var final1=[];
var final2=[];
var final3=[];
var complete=[];

var dsv = d3.dsv(" ", "text/plain");
dsv("/data/file.txt", function(error, data) {
  data.forEach(function(d) {
    final1.push({x: d.date, y: d.d1});
    final2.push({x: d.date, y: d.d2});
    final3.push({x: d.date, y: d.d3});
    ...
    complete.push(final1);
    complete.push(final2);
    complete.push(final3);
    ...
 });

That code works! But it's very laborious. How can i combine the arrays in an overall array, without the detour of generating a lots of help arrays (final1, final2, ...)?

So end up in an array as follows:

var complete=   [
[{'x':110522,'y':5},{'x':110523,'y':9},{'x':110524,'y':0}, ...],
[{'x':110522,'y':1},{'x':110523,'y':2},{'x':110524,'y':0}, ...],
...
];

Drew Gaynor · Accepted Answer · 2015-10-15 12:22:59Z

1

Use a for...in loop to iterate over each of the properties dynamically instead of explicitly handling each one.

var data = [
  { date: 110522, d1: 5, d2: 1, d3: 3, d4: 5, d5: 0, d6: 7 },
  { date: 110523, d1: 9, d2: 2, d3: 4, d4: 6, d5: 5, d6: 9 },
  { date: 110524, d1: 0, d2: 0, d3: 0, d4: 0, d5: 1, d6: 0 },
  { date: 110525, d1: 0, d2: 0, d3: 3, d4: 0, d5: 4, d6: 0 }
];

var results = [];

data.forEach(function (d) {
  var prop;
  var resultIndex = 0;
  
  for (prop in d) {
    if (d.hasOwnProperty(prop) && prop !== 'date') {
      if (!results[resultIndex]) {
        results[resultIndex] = [];
      }
      
      results[resultIndex].push({
        'x': d.date,
        'y': d[prop]
      });
      
      resultIndex++;
    }
  }
});

//Output for demonstration purposes
var element = document.createElement('pre');
element.innerHTML = JSON.stringify(results, null, 4);
document.body.appendChild(element);

edited Oct 15, 2015 at 12:22

answered Oct 14, 2015 at 23:20

Drew Gaynor

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8 Comments

RobG Over a year ago

Rather than for..in which requires a hasOwnProperty test (kudos for including it), consider using Object.keys(d).forEach(...). This seems like a candidate for reduce.

Drew Gaynor Over a year ago

@RobG Very true, keys would be cleaner. I think I've just written the for...in/hasOwnProperty pattern (especially in the days of supporting IE < 9) so many times that I default to that.

mcatis Over a year ago

'y': d[prop] - the y value isn't catch with this method.

Drew Gaynor Over a year ago

@user3265764 What do you mean by that? If you click "Run code snippet" in the answer you can see it working. Is your data object in a different format than what I show?

mcatis Over a year ago

shortly before this statement, a console.log(d[prop]) shows the correct values. but after filling the results array, y is 'undefined' or ""?

|

StackSlave · Accepted Answer · 2015-10-14 23:47:39Z

0

Your code could be more like:

var complete = [[],[],[]];
var dsv = d3.dsv(' ', 'text/plain');
dsv('/data/file.txt', function(error, data){
  for(var i=0,l=data.length; i<l; i++){
    var d = data[i];
    for(var n=0,q=complete.length; n<q; n++){
      complete[n].push({x:d.date, y:d['d'+(n+1)]});
    }
  }
});

answered Oct 14, 2015 at 23:47

StackSlave

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2 Comments

mcatis Over a year ago

does this only work for a fixed "complete"-array length?

StackSlave Over a year ago

No, as you can see the inner loop is based on complete.length.

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