Pull random string from array and insert in sentence

Question

How do I pull a string randomly from an array, and insert that string into a span? Heres the arrays:

var startupX = ['Uber', 'Google', 'Amazon', 'Apple', 'Facebook', 'Twitter'];
var startupY = ['Slack', 'Trello', 'Tesla', 'Hyperloop', 'Harvest'];

And these are the spans that a startup name needs to go into

<h1 id="xForY"></h1>
  <h1>A startup that is 
    <span id="startupX"></span>, but for 
    <span id="startupY"></span>
    </h1>

Which part are you having trouble with? Is it just the random part, or do you not know how to insert any text into a span using JS? — nnnnnn
– nnnnnn, Commented Jul 5, 2016 at 23:35
You can get your answer here: stackoverflow.com/questions/4550505/… — pokemon
– pokemon, Commented Jul 6, 2016 at 0:33

TimoStaudinger · Accepted Answer · 2016-07-05 23:26:37Z

1

First, find a random element from each of the arrays. Math.random() will help you with that.

Then you can use the DOM API to insert it into your page:

var startupX = ['Uber', 'Google', 'Amazon', 'Apple', 'Facebook', 'Twitter'];
var startupY = ['Slack', 'Trello', 'Tesla', 'Hyperloop', 'Harvest'];

var x = startupX[Math.floor(Math.random()*startupX.length)];
var y = startupY[Math.floor(Math.random()*startupY.length)];

document.getElementById('startupX').innerHTML = x;
document.getElementById('startupY').innerHTML = y;

<h1 id="xForY"></h1>
<h1>A startup that is 
    <span id="startupX"></span>, but for 
    <span id="startupY"></span>
</h1>

answered Jul 5, 2016 at 23:26

TimoStaudinger

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2 Comments

o.schiff. Over a year ago

This is great, to try and understand how it works tho-- innerHTML = x is taking the result of var x and replacing "startupX"?

TimoStaudinger Over a year ago

@OwenSchifferli It sets the inner HTML of the element with id startupX to the content of variable x.

BrunoLM · Accepted Answer · 2016-07-05 23:29:41Z

1

Math.random will give you a number from 0 inclusive to 1 exclusive [0, 1).

You can use that to get a random number that is within the max array index:

var randomIndex = Math.floor(Math.random() * startupX.length);

Then you can use this index to access your array:

startupX[randomIndex];

Having the value you can place it on the element:

document.getElementById('startupX').innerHTML = startupX[randomIndex];

answered Jul 5, 2016 at 23:29

BrunoLM

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