Javascript array not getting correct data

Question

I have a javascript if-else statement. It gets data from a websocket and depending on the condition being true or false enters the relevant branch.

But what I'm finding is that the data being added to both arrays is the same. This is the code:

 cities = JSON.parse(evt.data);
 if (cities.tag == 'red'){
 dataset.length = 0;
 console.log(cities.tag);
 for (var i = 0, item; item = buffer[i]; ++i) {
 buffer[i][1][0] = cities.clusters[item[0]] || 0;
 //console.log(buffer);
 dataset.push(buffer[i][1][0]);
 console.log('no1: ',dataset); 
 }
 }else{
 dataset2.length = 0;
 console.log(cities.tag);
 for (var i = 0, item; item = buffer2[i]; ++i) {
 buffer2[i][1][0] = cities.clusters[item[0]] || 0;
 dataset2.push(buffer2[i][1][0]);
 console.log('no2: ',dataset2); 
 } 
 }
 draw(); 

I know that it enters the correct branch and that the data is different, but somehow the code in the else branch just duplicates the array in the if branch.

I think theres must be something in the code, but I cannot see what.

Thanks

• Ryan Lynch: What do you mean by "duplicates the array"?
• user1869421: @RyanLynch; I mean dataset2 == dataset. dataset2, should have different data received through the websocket.
• bfavaretto: Where do you declare/define the arrays? If you have something like var dataset = [], dataset2 = dataset, that's the reason.
• Ryan Lynch: Do you do something like dataset = dataset2 = []; ?
• user1869421: I have declared two separate array: var dataset=[]; and var dataset2=[]

Answer 1

Read you code slowly and consider typing:

• For every item and index i of item in buffer:
  • set buffer2[i][1][0] to the value of cities.clusters[item[0]] or 0 if previous expression is not defined;

but see, there's a problem here already

If every every element at any given level of the buffer is supposed to be the same type, buffer2 is an array of array of arrays.

That means item is an array of arrays, and item[0] is an array, not an element. That, doesn't mean the statement won't work somehow, but, unless you are trying to win some sort of javascript obfuscation contest, that's not good code, and is likely not what was intended.

Edit: That really is a bizarre way of iterating through an array; maybe there exists some reason in this universe to iterate through an array that way, but if your array has any elements that would in some way evaluate to false, it wouldn't even iterate through all the elements.

Answer 2

Not able to understand your code fully as you have shown partial code. If most of the code is right, suggest swapping the array.push like this:

dataset.push(cities.clusters[item[0]] || 0);

dataset2.push(cities.clusters[item[0]] || 0);

This should work if buffer and buffer2 are not same.

• user1869421: Thanks....both buffer[] and buffer2[] are declared separatley and I replaced dataset2.push(buffer2[i][1][0]) and dataset.push(buffer[i][1][0]) with the above. But I still get the same result.
• closure: Please expand your question by showing us data in cities.clusters, buffer and buffer2. If each of these are array, a dump of console.log() would do, otherwise JSON.stringify()