CODEWITHSUNDEEP
javascriptmathrandom
Darienne Lake
Darienne Lake

Reputation: 13

Generate a random set from a limited set of chars in JavaScript using Math.random

I need to generate ~6 random characters using letters A-G and numbers 5-9. Can this be done using Math.random? They don't have to be unique every time. I have found this:

Math.floor(0|Math.random()*9e6).toString(36)

and it does work really well, but can I modify this to make it use certain characters (something like replace(/[^a-z]+/g, '') but in a more specific way) without adding arrays etc?

Edit: where is the fifth guy's answer?

Upvotes: 1

Views: 997

Answers (3)

CodeAt30
CodeAt30

Reputation: 884

You can totally use Math to pick random elements from the array (in this case the characters that will construct the random Id code) and concatenate those into the code string

steps:

  • first make an array with the "building" blocks of the code string.
  • then make an empty string to hold the codes string.
  • run a loop (number of times depends on how long you want the code to be)
  • Math Part: you need a random index. To do so you generate a random number using Math.random() which will give you something between 0-1. Then you multiply it by the length of the building blocks array, so that the result will be somewhere between 0 - array.length. Then you wrap this in Math.Floor to make sure you get a clean integer out of this process which will be your random index.
  • Then you simply add the random character to the codeString by picking array[randomIndex] and concatenating it to the codeString.
  • the loop will repeat istself and in the end you will have your codeString.

Code:

const array = ["A", "B", "C", "D", "E", "F", "G", "5", "6", "7", "8", "9"];
let codeString = "";

for(i=0 ; i<6 ; i++){
    const randomIndex = Math.floor(Math.random()* array.length);
    codeString = codeString + array[randomIndex];
}
console.log(codeString);

Upvotes: 2

Nina Scholz
Nina Scholz

Reputation: 386634

You could use different function with different factors and offsets for letters and numbers in the wanted range.

function getRandomLetter() { // A B C D E F G
    return Math.floor(Math.random() * 7 + 10).toString(36).toUpperCase();
    //                                ^       count of wanted letters
    //                                    ^^  offset for the first letter, to get A
    //                                        with a random result of zero
}

function getRandomNumber() { // 5 6 7 8 9
    return Math.floor(Math.random() * 5 + 5).toString(36);
    //                                ^      9 - 5 + 1 or count, as factor
    //                                    ^  offset 
}
    
console.log(getRandomLetter());
console.log(getRandomNumber());

Upvotes: 2

Deepak Kamat
Deepak Kamat

Reputation: 1980

If the pattern of the random characters appearing isn't very important then I would do something like this

// This function helps us generate a random number between two numbers. 
function random(min, max) {
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

// The characters we need
var characterArray = ["A", "B", "C", "D", "E", "F", "G", 1, 2, 3, 4, 5, 6, 7, 8, 9];

// Now run a loop six times, get a random number between 0 and the length of the characterArray and concatenate it into a new variable

var randomString = "";
for ( var i = 0; i < 6; i++) {
    randomString += characterArray[ random(0, characterArray.length - 1) ];
}

console.log( randomString );

The code can be shortened even further for e.g instead of actually making an array of characters, we can assign a string characterArray = "ABCDE...7,8,9" as a string is also an array of characters and serves the purpose similarly, but I thought it would be a good idea to write it in a way that is self-explanatory for you to understand and add or change anything in the code as you like.

With a function to give us a random number between two numbers, we can use an array that contains all the characters that our result can have. Then, since we want to get a random number with 6 different characters we use a for loop, run it six times, each time it gets a random element from the array of characters, and does the job.

Upvotes: 0

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