Search for item in array with Javascript

Question

I am trying to add some code where the user clicks a button and the code generates 3 numbers (none repeating, so 245 is OK but 122 and 121 is not) and display them onscreen, one each second. To ensure there are no repeats, I am using an array: var usedNums = []; . Then, I create the number ( digit = Math.random() ) and check if it is already in the array, and if it's not, add it, like this:

if ($.inArray(digit, usedNums) !== -1) {
        newNums();
    } else {
        usedNums.push(digit);
        $('#memDigit').html(digit);

}

The first few times, it works, but when I click it for the 10th time, I get the Uncaught RangeError: Maximum call stack size exceeded error. Help!

Here's the full code:

var usedNums = [];
var digit;
var amount = 3;

function newNums() {
    digit = Math.floor(Math.random() * 10);
    if ($.inArray(digit, usedNums) !== -1) {
        newNums();
    } else {
        usedNums.push(digit);
        $('#memDigit').html(digit);

    }

}

function createNums() {
    for (var i; i < amount; i++) {
        setTimeout(newNums, 1000);
    }
}

//$(document).ready(createNums);

Answer 1

我认为您应该在每个数字生成完成后清空/重新初始化usedNums数组。

Answer 2

If IE <= 10 is not a concern, you may want to take advantage of crypto.getRandomValues to do this in one shot instead.

The getRandomValues method fills a TypedArray with a series of random values in the range supported by that array type. If we ask for 10 of these vales, we now have, in effect, a hash of the numbers 0-9 (that is, the indices of the array) pre-associated with random values for sorting by (the values). The result will be both more random and — unlike the 'already seen this value, try again' pattern — it should run in constant time.

ES6:

const nums = [ ...crypto.getRandomValues(new Int16Array(10)) ]
  .map((sortVal, num) => [ sortVal, num ])
  .sort(([ a ], [ b ]) => a < b ? -1 : Number(a > b))
  .map(([ , num ]) => num)
  .slice(0, 3);

ES5:

var nums = [].slice.call(crypto.getRandomValues(new Int16Array(10)))
  .map(function(sortVal, num) { return [ sortVal, num ]; })
  .sort(function(a, b) { return a[0] < b[0] ? -1 : Number(a[0] > b[0]); })
  .map(function(pair) { return pair[1]; })
  .slice(0, 3);

Breakdown:

• new Int16Array(10) creates an empty TypedArray of length 10
• crypto.getRandomValues(...) fills that array with random values
• We convert the result to a regular array
• We map that to [ randomVal, index ] tuples
• We sort that by the random value (remembering to coerce to Number explicitly, to cover the Safari sort implementation bug)
• We map down to just the index — ie, a number from 0-9
• We grab just the first three values