# Randomly select file to preload (p5.js)
**URL:** https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148
**Category:** Coding Questions
**Created:** [July 10, 2021, 9:55am UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148 "2021-07-10T09:55:29Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@fleshcircuit](https://discourse.processing.org/u/fleshcircuit)
#### Post date: [July 10, 2021, 9:55am UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/1 "2021-07-10T09:55:29Z")
I am working on a project where I am using data from a json file, but I am wondering if it is possible to randomly select a file from the data folder for a sketch to use. I don’t want to load all the files, since I fear that will slow down the sketch. In my case, I will have 90 different json files in the data folder, but I want only one selected at random to preload and use in the sketch.
---
### Author:  [@Chrisir](https://discourse.processing.org/u/Chrisir)
#### Post date: [July 10, 2021, 12:00pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/2 "2021-07-10T12:00:38Z")
when you know the names in forehand just make a list
```auto
String[] list1 = {
"name1",
"name2",
....
};
```
and then create a random number and load the file indicated in the list1 at the position of the number index
Chrisir
P.S.
in standard processing you’d use file.list() but I don’t know the equivalent in p5.js
```auto
StringList inventory;
//---------------------------------------------------------------------------
// processing core functions
void setup() {
size(880, 800);
background(111); // gray
}
void draw() {
background(111); // gray
updateList();
showList();
}
//---------------------------------------------------------------------------
// Other functions
void updateList() {
File file = new File(dataPath(""));
String[] fileList = file.list();
if (fileList==null) {
println("Folder is empty.");
} else {
// success
inventory = new StringList();
for (String s1 : fileList) {
inventory.append(s1);
}
inventory.sort();
}//else
}//func
void showList() {
if (inventory==null)
return; // leave
int i=0;
for (String s1 : inventory) {
text(s1, 33, 44+i*22);
i++;
}//for
//
}//func
//
```
---
### Author:  [@fleshcircuit](https://discourse.processing.org/u/fleshcircuit)
#### Post date: [July 14, 2021, 9:47am UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/3 "2021-07-14T09:47:15Z")
Thanks. I created a txt file with the file names, which I preloaded as a string. I then ran into trouble trying to then use that to determine what JSON file to load.
```auto
let heartRate;
let list1;
function preload(){
list1 = loadStrings('glidDriveList.txt');
}
function setup() {
createCanvas(windowWidth, windowHeight);
colorMode(HSB, 360, 100, 100, 100);
frameRate(20);
num = height*.3;
console.log(list1);
let day = random(131);
heartRate = loadJSON(list1[day]);
//heartRate = loadJSON('data/heart_rate-2020-05-01.json')
```
The sketch is working correctly when I directly indicate what file to load (commented out), but not when I try to get a name from the string array. File names also appear to be correctly loaded into array when viewed in console.
---
### Author:  [@fleshcircuit](https://discourse.processing.org/u/fleshcircuit)
#### Post date: [July 14, 2021, 10:11am UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/4 "2021-07-14T10:11:35Z")
Figured it out! I just needed to put int around the random number:
```auto
let day = int(random(0,131));
heartRate = loadJSON(list1[day]);
```
---
### Author:  [@Chrisir](https://discourse.processing.org/u/Chrisir)
#### Post date: [July 14, 2021, 12:24pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/5 "2021-07-14T12:24:25Z")
> [@fleshcircuit](#):
>
> `glidDriveList.txt`
we don’t know the content of this
does it look like this:
```auto
'data/heart_rate-2020-05-01.json'
```
or is **data/** missing or even **.json** mssing?
---
### Author:  [@Chrisir](https://discourse.processing.org/u/Chrisir)
#### Post date: [July 14, 2021, 12:26pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/6 "2021-07-14T12:26:02Z")
> [@fleshcircuit](#):
>
> `(list1[day]);`
does println (list1[day]); work?
Do you have to wait until preload() is finished or does this happen automatically?
---
### Author:  [@fleshcircuit](https://discourse.processing.org/u/fleshcircuit)
#### Post date: [July 14, 2021, 12:39pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/7 "2021-07-14T12:39:19Z")
Here are samples of the file names in glidDriveList.txt:
```auto
data/heart_rate-2020-05-01.json
data/heart_rate-2020-05-02.json
data/heart_rate-2020-05-03.json
data/heart_rate-2020-05-04.json
```
---
### Author:  [@fleshcircuit](https://discourse.processing.org/u/fleshcircuit)
#### Post date: [July 14, 2021, 12:39pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/8 "2021-07-14T12:39:39Z")
Yes, the println works.
---
### Author:  [@Chrisir](https://discourse.processing.org/u/Chrisir)
#### Post date: [July 14, 2021, 12:42pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/9 "2021-07-14T12:42:57Z")
> [@fleshcircuit](#):
>
> `heartRate = loadJSON(list1[day]);`
did you try `heartRate = loadJSON(list1[day].trim());`
---
### Author:  [@Chrisir](https://discourse.processing.org/u/Chrisir)
#### Post date: [July 14, 2021, 12:46pm UTC](https://discourse.processing.org/t/randomly-select-file-to-preload-p5-js/31148/10 "2021-07-14T12:46:31Z")
ah, you got it! great!