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# How To Create An Unique And Random Number From An Array In Javascript

## 12 January 2022 - 1 answer

i'm a super beginner in JS. I try to create a way to generate random unique number (between 0 and 10) by clicking on a button. I want that this number is delete from the array after appearing.

Thank you 🙏🏻

``````const btn = document.getElementById("btn");

const showNumber = document.querySelector("h2");

let allNumbers = [];
for (var i =1; i <= 10; i++){
allNumbers.push(i);
}

const randomNumber = btn.addEventListener('click',()=> {
let n = Math.floor(Math.random()*allNumbers.length+1);
showNumber.innerText = n;

});

if(allNumbers.indexOf(n+1) === n) {
allNumbers.splice(n-1,1);
};
``````
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## Answer

I'm assuming that you want the button to be able to work multiple times, and that you must therefore be able to remove a number from the array no matter where it might be located, as their positions will shift as numbers are removed. You therefore have several problems:

• The code that selects a random number to remove may choose a number that has already been removed.
• The code assumes that the number is at a particular position, which may not be true after the first removal.
• The code that removes the element from the array is currently located outside of the event listener that is invoked when you click the button; you must move it inside the function for it to work.

To avoid the first problem, instead of choosing a random number from 1 to 10 to remove, select a random location in the array:

``````const index = Math.floor(Math.random() * allNumbers.length);
const n = allNumbers[index];
``````

Then you can just remove that element by index:

``````allNumbers.splice(index, 1);
``````

Also note that `randomNumber` is not useful because `addEventListener()` only ever returns `undefined`.

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source: stackoverflow.com
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