Ensure uniqueness in an array after index 0

Asked Mar 25 '19 at 10:24

Active Mar 25 '19 at 10:29

Viewed 45 times

Given this code:

random: function() {
  return Math.floor(Math.random() * 100 + 1)
}

let result = []

result.push(random()) // it doesn't matter if this integer is pushed again in the next line
[...Array(10)].forEach((_, i) => result.push(random())) // all of these have to be unique

How can I make sure that no duplicates are pushed to result except possibly the first while maintaining the length of the array at 11?

edited Mar 25 '19 at 10:29

asked Mar 25 '19 at 10:24

t56k

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9
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115

Use [Array.prototype.indexOf()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf) - check that it is -1 before pushing. – Reinstate Monica Cellio Mar 25 '19 at 10:26
Why except the first? That would never be a dupe – mplungjan Mar 25 '19 at 10:26
Your array could theoretically contain only 2 elements, right? – goodvibration Mar 25 '19 at 10:26
@goodvibration It should have 11 according to this code. – t56k Mar 25 '19 at 10:27
2

Well, your definition does not imply this fact. – goodvibration Mar 25 '19 at 10:27
You would have to loop until you had 10 unique numbers. Now you only loop 10 times – mplungjan Mar 25 '19 at 10:28
So in a nutshell: how to generate 10 unique random numbers and then one more which we don't care about…? – deceze Mar 25 '19 at 10:28
3

Given the numbers are in the range 1 to 100, you can start with an array of 1 to 100 and randomly *splice* 10 values from it. – RobG Mar 25 '19 at 10:29
3

shuffle and slice and evrything nice ;) – mplungjan Mar 25 '19 at 10:29
1

Take `arr = [1,2,...,100]` and use `Math.random()` in order to shuffle it. Then use `arr.slice(0,10)` and add a random value between 1 and 100 at the beginning of it. – goodvibration Mar 25 '19 at 10:30
Why do you need to maintain the length of the array (within the array itself) when the language already does that for you? – MikeB Mar 25 '19 at 10:32

Ensure uniqueness in an array after index 0

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