Assistance with Javascript for each loop

Question

I am trying to get my program to generate a 4 number pin to be used for a game.

I originally wanted to do this:

function paswdGen() {
    var nums = [0, 0, 0, 0];
    for each (var x in nums) {
        x = Math.floor((Math.random() * 9) + 1);
    }
} 
document.getElementById("nums").innerHTML = nums;

How do I use a "for each" loop in javascript without jQuery?

http://stackoverflow.com/questions/9329446/for-each-over-an-array-in-javascript — user1983983, Feb 05 '15 at 15:43
Just to point out your number generator can create nr 10 and will not create 0. — DeadAlready, Feb 05 '15 at 15:46
There's no way it'll generate a 10. The return value of `Math.random()` is strictly less than 1. This will result in a value between 1 and 9. — Phylogenesis, Feb 05 '15 at 15:56

score 1 · Answer 1 · answered Feb 05 '15 at 15:44

1

You'll want to use the language feature Array.prototype.forEach. Check out some great documentation from MDN here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

Here's a version of your code:

var nums = [0, 0, 0, 0];
nums.forEach(function(nums){
    x = Math.floor((Math.random() * 9) + 1);
})

answered Feb 05 '15 at 15:44

Thomas Murphy

1,360
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I should also add that this method call is Array-specific. There is separate functionality for object and string iteration. – Thomas Murphy Feb 05 '15 at 15:45
I used this but it just returned an undefined if I used something like: `document.getElementById("nums").innerHTML = nums[0];` Any advice? – Roman P Feb 05 '15 at 16:00

score 1 · Answer 2 · answered Feb 05 '15 at 15:50

I think Array.prototype.forEach may not be what you need here, may I suggest using Array.prototype.map instead? (Note that this would work on most browsers and IE9+)

// this function would return a string of 4 digits
function paswdGen() {
    var nums = [0, 0, 0, 0];

    return nums.map(function () {
        return Math.floor((Math.random() * 9) + 1);
    }).join('');
}

score 0 · Answer 3 · answered Feb 05 '15 at 15:48

var code = '';

for (var i = 0; i < 4; i++) {

    code += Math.floor((Math.random() * 9) + 1);
}

console.log(code); // Outputs 1234 (for example)

If your goal is to do it with a forEach:

var nums = [0, 0, 0, 0];
var code = '';

nums.forEach(function(){
    code += Math.floor((Math.random() * 9) + 1);
})

console.log(code); // Outputs 1234 (for example)

andrusieczko · Answer 4 · 2015-02-05T15:59:14.543

0

no need to create the array manually:

var length = 4;
var range = 10;

Array.apply(null, {length: length}).map(function() {
  return Math.floor((Math.random() * range) + 1);
});

An alternative way:

var length = 4;
var range = 10;
var transform = function(random) { return Math.floor(random * range) + 1 };
Array.apply(null, {length: length}).map(Math.random).map(transform)

edited Feb 05 '15 at 15:59

answered Feb 05 '15 at 15:53

andrusieczko

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Assistance with Javascript for each loop

4 Answers4