As an exercise to help learn JS, I wrote a short bit of code that defines an array of random integers and then randomly logs one of them. Here's the code:

var turkey = true
var crud = []

for (i=0;i<10;i++)   {
    j = abs(Math.random()* 10);

while (turkey)  {
    turkey = false;

This code returns a syntax error saying abs is not defined. I think I need to import a module but am not sure which one or how. Some help?

Also, if there's a more elegant way to do what I'm doing here, all input is welcome. :)

4 Years
Discussion Span
Last Post by Proglearner

Any point in just importing Math? It would be more overhead, but would simplify the code in the absence of other modules.

EDIT: Here's another snippet that returns a syntax error:

var oneVar = true;
var oneString;
var oneArray = [];

for (i=0;i<10;i++)   {
    j = Math.abs(Math.random() * 10);

while (oneVar)  {
    oneString=String(oneArray[Math.abs(Math.random() * 10)]);
    oneVar = false;

do  {
}   while (oneVar);

So what's wrong with this?

Edited by Proglearner: adding info


My solution would use the Math.random too - couldn't find a good alternative. I used this to provide an alternative other Math.* functions: http://bit.ly/TTua1H

//Function similar to range() in PHP - modded from http://bit.ly/MlBd05
Array.range = function(from, to, increment){
    var A = [];
    if(typeof from == 'number'){
        A[0]= from;
        increment = increment || 1;
        while(from + increment <= to){
            A[A.length]= from += increment;
    return A;

pool = Array.range(17,24,1); //Array 17,18,19...24
numItems = pool.length;
randomKey = Math.random() * numItems | 0; // this is the bitop

document.write('The array contains: {' + pool.join(', ') + '}<br />');
document.write('Random key: ' + randomKey + ' (0-based) and the value: ' + pool[randomKey] + '<br />');

For testing randomness, you could do soemthing like this:

pool = Array.range(17,24,1); //from the previous code - Array.range...

numItems = pool.length;
counterArray = Array();
for(i=0;i<numItems;i++)  counterArray[i] = 0;

document.write('The array contains: {' + pool.join(', ') + '}<br />');

    randomKey = Math.random() * numItems | 0;
    //document.write('Random key: ' + randomKey + ' (0-based) and the value: ' + pool[randomKey] + '<br />');

document.write('The totals of each key are: {' + counterArray.join(', ') + '}<br />');

Edited by diafol


I'm studying this code, diafol, and it uses a ton of notation I don't know. typeof I can figure out, but the double pipe means "or," doesn't it? How does that work here? The <= is something I don't know, either. The use of the pipe on line 16 is also something I don't understand. Lines 18 and 19 also seem to contain XML rather than JS. Please elaborate.



Lines 18/19 are just to display to the screen

double pipe || is or to set the increment to 1 if it's not set

You can forget the Array.range bit if you want - it was just an easy way to create an array in the first place.

from + increment <= to

Just means - keep doing it until (from + increment) is less or equal to 'to'

The pipe (line 16) is the bit operator - it's a quicker way of doing:

Math.floor or Math.abs as can be seen here: http://bit.ly/TTua1H


@Proglearner, Your script is not working...

1)Line 6, j = Math.abs(Math.random() * 10);, the Math.abs() does nothing for you. The value returned from Math.random() is between 0 and 1 (a float), so it is always a positive number anyway.

2)Line 11, oneString=String(oneArray[Math.abs(Math.random() * 10)]); would almost always produce undefined. (Also Math.abs() does nothing for you either.) The reason is that Math.random() returns a float value between 0 and 1 and most likely not to be able to multiply with your selected number and produces an integer (number). An array index is an integer (number) which has no decimal. As a result, you attempt to access a non-existing array index.

// i.e.
var rand = Math.random() * 10;
// let say Math.random() returns 0.23453
// now your rand is 2.3453
// as a result, an array of array[rand] will give you "undefined" value

What you need to do is to use Math.floor() which truncates any decimal produced by the Math.random().

oneString = String(oneArray[Math.floor(Math.random()*10)])

Edited by Taywin

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