CODEWITHSUNDEEP
javascriptjqueryarrays
user1869421
user1869421

Reputation: 837

Javascript resetting an array

I'm having with some very strange behaviour when I try to reset an array; eg:

data.length=0;

where data is an array. I'll try and include only the relevant code here but basically what I;m doing is on each iteration of my program I'm populating the array with updated values and the array then is used in another function. But when I reset the array the function appears to get the values on the first iteration but none afterwards.

However when I don't reset the array then the function gets the values, but also the older values. I don't want this, as I only want the new updated values only. This is a code snippet:

      var buffer = [['1',[0]],['2',[0]],['3',[0]],['4',[0]]];
      var dataset = [];

         ws.onmessage = function(evt){ 
         dataset.length=0;
         var distances = JSON.parse(evt.data);

         console.log(distances);

            for(var i=0; i<buffer.length; i++) {
                if(buffer[i][0] == distances.miles) {
                    buffer[i][1][0]++;
                    }
                //console.log(buffer);

                dataset.push(buffer[i][1][0]);
                draw();
                //console.log(dataset); 

            }

    }

The function uses the dataset array to redraw a chart.

I've tried to keep it simple here, but the full function is here.

I really don't know what's causing this unexpected behaviour.

EDIT:

console.log(dataset) shows the new updated values, but somehow dataset.length=0; is preventing the updated array to be used by the draw() function. As without the resetting of the array the array can be used by the draw() function.

EDIT:

I've tried to not reset the array but instead get the last 4 elements and put them in a new array and then send them to the draw(), but still the same odd behaviour:

            x = dataset.slice(-4);
            console.log(x);
            draw();

But if I don't do that or don't clear the array, then draw() render a 'wrong' chart. I can't see what is wrong.

THE problem somehow seems to reside with the resetting of the array and that because of this it means the draw() function appears to be called only once at the first iteration.

Please, Please help

Upvotes: 1

Views: 3136

Answers (2)

hvgotcodes
hvgotcodes

Reputation: 120198

Looking at your code, I'm not sure, but why do you even have dataset? You don't ever read anything out of it, and you say you want to clear it every time thru the array.

Do you mean do to something like:

for(var i=0; i<buffer.length; i++) {
    if(buffer[i][0] == distances.miles) {
        buffer[i][1][0]++;
    }
    dataset.push(buffer[i][1][0]);
}
draw(dataset); // draw outside the loop, using dataset.

Upvotes: 1

coolguyxp
coolguyxp

Reputation: 31

You don't need to set length at all. To clear a list of all value, just set it to an empty list:

dataset = [];

Upvotes: 2

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