Javascript string to object error? random array var not aloowed

Question

I want create a array from array by random, but I'm starting on javascript. Here is my question.

//array
var t = ["house","pen","table","eletronic"];

//-> selected a name option 0

var w = t[0]; // selected

var x = w;
var y = 0 to 3; // random

var house =["red","blue","orange","black"];
var pen   =["silver", "gold", "cooper","plastic"];
var table =["marble","oak","yep","pine"];
var eletro=["computer","mobile","mac","tablet"];


// what i wish
var z = house[0]; // return red  // x = typeof return object

//x this is the error type string not recognize list array query
var z = x[y]; // x = typeof return string 
var z = "house"[0]; // return h - return string - not object

//after make a default

var a = x[y]; //y != y
var b = x[y]; //y != y

document.getElementById("demo1").innerHTML=z; // blue house;
document.getElementById("demo2").innerHTML=a; // silver pen;
document.getElementById("demo3").innerHTML=b; // marble table;

<p id "demo1"></p>
<p id "demo2"></p>
<p id "demo3"></p>

I think I must convert double quotes - "house" - string to object - house - to convert to a var and before feed the system?

Answer 1

I'm not 100% sure what you're asking here, but the behaviour i believe you want can be accomplished using 2d arrays as such -

const t = [["red","blue","orange","black"], ["silver", "gold", "cooper","plastic"], ["marble","oak","yep","pine"], ["computer","mobile","mac","tablet"]]

const [rand1, rand2] = [Math.floor(Math.random() * t.length), Math.floor(Math.random() * t[0].length)]
console.log(t[rand1][rand2])

Answer 2

You could use the eval() function to obtain the object reference, but it could lead to hairy problems so it would better use another option like for example a switch statement:

//array
var t = ["house","pen","table","electronic"];

var house = ["red","blue","orange","black"];
var pen = ["silver", "gold", "cooper","plastic"];
var table = ["marble","oak","yep","pine"];
var electronic = ["computer","mobile","mac","tablet"];

var w = Math.floor(Math.random() * 3); // random type index (0 to 3)
var x = t[w]; // name of the random type
var y = Math.floor(Math.random() * 3); // random option (0 to 3)

switch (w) { // use the appropriate object based on type index
  case 0: z=house[y]; break;
  case 1: z=pen[y]; break;
  case 2: z=table[y]; break;
  case 3: z=electronic[y]; break;
}
console.log(w, z);
var z = z + ' ' + x // appending "house" to color
console.log(z);

document.getElementById("demo1").innerHTML=z;

<p id="demo1"></p>
<p id="demo2"></p>
<p id="demo3"></p>

Answer 3

It's not quite clear to me if this is what you're looking for, but one solution might be to structure your data so that it's easier to get at:

const items = {
  house: ["red","blue","orange","black"],
  pen: ["silver", "gold", "cooper","plastic"],
  table:  ["marble","oak","yep","pine"],
  eletro: ["computer","mobile","mac","tablet"]
}

const randomChoice = list => list[Math.floor(list.length * Math.random())]

const randomObject = (items) => {
  const itemType = randomChoice(Object.keys(items))
  const modifier = randomChoice(items[itemType])
  return `${modifier} ${itemType}`
}

randomObject(items) //=> "marble table" or "plastic pen", etc.

Update

The comment asked to pick a random element of a certain type. This variation would allow for that:

const randomOfType = (items, itemType) => {
  const modifier = randomChoice(items[itemType])
  return `${modifier} ${itemType}`
}

const randomObject = (items) => randomOfType(items, randomChoice(Object.keys(items)))

randomOfType(items, 'table') //=> "oak table" or "marble table", etc.