How can I use a for loop to extract a string of characters from an array in .js

C Dub 0
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I am new to javaScript and having a terrible time with understanding loops. Currently I have a random text generator function. I have gotten it to generate random characters from a string but only one character each time the function is ran. I would like to build a string of 20 random characters from the output of the function.

This is what I have so far:

function passGen() {
    let text = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVVWYXZ()!@#$%&*/?+-%".split("");
    let randomIndex = Math.floor(Math.random() * text.length);
    return text[randomIndex];
}
let randomPass = passGen();

I would like to let the function produce the random character and then use a for loop to out put 20 of these random characters in a string.

I can't get

for (let i = 0; i <= 20; i++){
console.log(randomPass)

to work.

Any help is appreciated.

random for-loop arrays javascript
2 Answers

You need to define a string variable and then use a loop to append characters to it, like this:

function passGen () {
  const text = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVVWYXZ()!@#$%&*/?+-%'.split('')
  let res = ''
  for (let i = 0; i < 20; i++) {
    res += text[Math.floor(Math.random() * text.length)]
  }
  return res
}
const randomPass = passGen();
Jannchie0

You need to specify for yourself what characters you want to support, for example:

function getRandomCharacter(supportedCharacters) {
    return supportedCharacters[parseInt(Math.random() * supportedCharacters.length)];
}

function getRandomString(supportedCharacters, length) {
    let output = "";
    while (length--) output += getRandomCharacter(supportedCharacters);
    return output;
}

console.log(getRandomString([
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
    'U', 'V', 'W', 'X', 'Y', 'Z',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
    'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
    'u', 'v', 'w', 'x', 'y', 'z',
], 20));

  • getRandomCharacter randomizes a character
    • Math.random() generates a real number which is greater or equal than 0 but smaller than 1
    • multiplying Math.random() with the number of supported characters scales the value to the interval between [0, length)
    • parseInt rounds the result down
    • the result of parseInt can be used as an index
  • getRandomString generates all the characters using a while loop
    • length-- evaluates length and then decreases it by 1
    • += concatenates the resulting character to output
    • return output; clarifies that the result of the function is the string
  • the test sample defines an array (you could do it with a string as well if you want) of the characters you want to support and the length of the string you desire
Lajos Arpad0
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