How do I select a random object(?) from a JSON file with Javascript?

Question

In my Discord Bot that I am making, it needs to select a random object from a JSON file. My current code is this:

    function spawn(){
        if (randomNum === 24) return
        const name = names.randomNum
        const embed = new Discord.RichEmbed()
        .setTitle(`${name} has been found!`)
        .setColor(0x00AE86)
        .setThumbnail(`attachment://./sprites/${randomNum}.png`)
        .setTimestamp()
        .addField("Quick! Capture it with `>capture`!")
        msg.channel.send({embed});
    }

The JSON file looks like this:

{
    "311": "Blargon",
    "310": "Xryzoz",
    "303": "Noot",
    "279": "",
    "312": "Arragn",
    "35": "Qeud",
    ...
}

I want it to pick a random one of those, such as 303, and post it in a rich embed. What do I do from here?

Please note that 303 is a property of an object, not an actual object. — connexo
– connexo, Commented Apr 6, 2018 at 3:38
Does this answer your question? "Pick random property from a Javascript object", "Creating an array from files in a folder and sending them randomly" — outis
– outis, Commented Nov 5, 2021 at 20:32

Steve Holgado · Accepted Answer · 2018-04-06 07:45:10Z

7

You can select a random name like this:

// Create array of object keys, ["311", "310", ...]
const keys = Object.keys(names)

// Generate random index based on number of keys
const randIndex = Math.floor(Math.random() * keys.length)

// Select a key from the array of keys using the random index
const randKey = keys[randIndex]

// Use the key to get the corresponding name from the "names" object
const name = names[randKey]

// ...

edited Apr 6, 2018 at 7:45

answered Apr 6, 2018 at 7:14

Steve Holgado

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Comments

intentionally-left-nil · Accepted Answer · 2018-04-06 03:49:44Z

3

const jsonData = {
    "311": "Blargon",
    "310": "Xryzoz",
    "303": "Noot",
    "279": "",
    "312": "Arragn",
    "35": "Qeud",
}
const values = Object.values(jsonData)

const randomValue = values[parseInt(Math.random() * values.length)]

console.log(randomValue)

edited Apr 6, 2018 at 3:49

intentionally-left-nil

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answered Apr 6, 2018 at 3:34

connexo

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Comments

Rohit Nandi · Accepted Answer · 2018-04-06 09:48:59Z

0

This can be done in two steps

Loading Json file using Javascript and local server

1> Create a Json file, name it botNames.json, add your data.

Note: .json files can only contain Json Object, Array or Json literal

{
    "311": "Blargon",
    "310": "Xryzoz",
    "303": "Noot",
    "279": "",
    "312": "Arragn",
    "35": "Qeud"
}

Use XMLHttpRequest() to load the data, you can use below function to load the .json file passing a callback function and the path as an argument.

function loadJSON(callback,url) {   
  var xobj = new XMLHttpRequest();
  xobj.overrideMimeType("application/json");
  xobj.open('GET', url, true); 
  xobj.onreadystatechange = function () {
        if (xobj.readyState == 4 && xobj.status == "200") {
          callback(xobj.responseText);
        }
  };
  xobj.send(null);
}

To generate a random index you can use the below expression

Math.floor(lowerLimt + (upperLimit - lowerLimit+1)*Math.Random())

this will give you values in the range [lowerLimit,upperLimit)

Note: This is possible because Math.random() generates a fractional number in the range [0,1)

Your callback function will be

function callback1(response){
        var botNames = JSON.parse(response)
        var keys = Object.keys(botNames);
        var randomProperty = keys[Math.floor(keys.length*Math.random())]
        var botName = botNames[randomProperty]
        console.log(botName);
    }

You can use above concepts in your code as

function loadJSON(callback,url) {   
    var xobj = new XMLHttpRequest();
    xobj.overrideMimeType("application/json");
    xobj.open('GET', url, true); 
    xobj.onreadystatechange = function () {
            if (xobj.readyState == 4 && xobj.status == "200") {
            // sending the resonse to your callback
            callback(xobj.responseText);
            }
    };
    xobj.send(null);
}

function spawn(){
        loadJSON(function(response){
          //This is your callback function

          var names = JSON.parse(response)
          var keys = Object.keys(botNames);
          var randomNum = keys[Math.floor(keys.length*Math.random())]
            
          if (randomNum === 24) return
          const name = names[randomNum]
          const embed = new Discord.RichEmbed()
          .setTitle(`${name} has been found!`)
          .setColor(0x00AE86)
          .setThumbnail(`attachment://./sprites/${randomNum}.png`)
          .setTimestamp()
          .addField("Quick! Capture it with `>capture`!")
          msg.channel.send({embed});
        },'/PATH_TO_YOUR_JSON/botNames.json')
    }

answered Apr 6, 2018 at 9:48

Rohit Nandi

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4 Comments

jackmerrill Over a year ago

I tried what you did there, and I got this error: TypeError: xobj.overrideMimeType is not a function

Rohit Nandi Over a year ago

It works for me, I tried with python and nodeJs servers, in Chrome,IE. Can you give some inputs like which server, browser and software versions you are using? I got a post on similar problem, posted yesterday stackoverflow.com/questions/49675273/…

Rohit Nandi Over a year ago

Info Across the internet: If using IE, It is only supported in IE11 and later. You can omit that line, it will still work, with the default server provided MIME type eg. 'text/plain'

Rohit Nandi Over a year ago

One more alternative you can safe guard it by using if (xobj.overrideMimeType) { xobj.overrideMimeType( 'application/json' ); }

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