There are some examples on the Mozilla Developer Network page:
/**
* Returns a random number between min (inclusive) and max (exclusive)
*/
function getRandomArbitrary(min, max) {
return Math.random() * (max - min) + min;
}
/**
* Returns a random integer between min (inclusive) and max (inclusive).
* The value is no lower than min (or the next integer greater than min
* if min isn't an integer) and no greater than max (or the next integer
* lower than max if max isn't an integer).
* Using Math.round() will give you a non-uniform distribution!
*/
function getRandomInt(min, max) {
min = Math.ceil(min);
max = Math.floor(max);
return Math.floor(Math.random() * (max - min + 1)) + min;
}
Here's the logic behind it. It's a simple rule of three:
Math.random()
returns a Number
between 0 (inclusive) and 1 (exclusive). So we have an interval like this:
[0 .................................... 1)
Now, we'd like a number between min
(inclusive) and max
(exclusive):
[0 .................................... 1)
[min .................................. max)
We can use the Math.random
to get the correspondent in the [min, max) interval. But, first we should factor a little bit the problem by subtracting min
from the second interval:
[0 .................................... 1)
[min - min ............................ max - min)
This gives:
[0 .................................... 1)
[0 .................................... max - min)
We may now apply Math.random
and then calculate the correspondent. Let's choose a random number:
Math.random()
|
[0 .................................... 1)
[0 .................................... max - min)
|
x (what we need)
So, in order to find x
, we would do:
x = Math.random() * (max - min);
Don't forget to add min
back, so that we get a number in the [min, max) interval:
x = Math.random() * (max - min) + min;
That was the first function from MDN. The second one, returns an integer between min
and max
, both inclusive.
Now for getting integers, you could use round
, ceil
or floor
.
You could use Math.round(Math.random() * (max - min)) + min
, this however gives a non-even distribution. Both, min
and max
only have approximately half the chance to roll:
min...min+0.5...min+1...min+1.5 ... max-0.5....max
└───┬───┘└────────┬───────┘└───── ... ─────┘└───┬──┘ ← Math.round()
min min+1 max
With max
excluded from the interval, it has an even less chance to roll than min
.
With Math.floor(Math.random() * (max - min +1)) + min
you have a perfectly even distribution.
min.... min+1... min+2 ... max-1... max.... max+1 (is excluded from interval)
| | | | | |
└───┬───┘└───┬───┘└─── ... ┘└───┬───┘└───┬───┘ ← Math.floor()
min min+1 max-1 max
You can't use ceil()
and -1
in that equation because max
now had a slightly less chance to roll, but you can roll the (unwanted) min-1
result too.
Numbers
[...Array(5).keys()];
=> [0, 1, 2, 3, 4]
Character iteration
String.fromCharCode(...[...Array('D'.charCodeAt(0) - 'A'.charCodeAt(0) + 1).keys()].map(i => i + 'A'.charCodeAt(0)));
=> "ABCD"
Iteration
for (const x of Array(5).keys()) {
console.log(x, String.fromCharCode('A'.charCodeAt(0) + x));
}
=> 0,"A" 1,"B" 2,"C" 3,"D" 4,"E"
As functions
function range(size, startAt = 0) {
return [...Array(size).keys()].map(i => i + startAt);
}
function characterRange(startChar, endChar) {
return String.fromCharCode(...range(endChar.charCodeAt(0) -
startChar.charCodeAt(0), startChar.charCodeAt(0)))
}
As typed functions
function range(size:number, startAt:number = 0):ReadonlyArray<number> {
return [...Array(size).keys()].map(i => i + startAt);
}
function characterRange(startChar:string, endChar:string):ReadonlyArray<string> {
return String.fromCharCode(...range(endChar.charCodeAt(0) -
startChar.charCodeAt(0), startChar.charCodeAt(0)))
}
lodash.js _.range()
function
_.range(10);
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
_.range(1, 11);
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
_.range(0, 30, 5);
=> [0, 5, 10, 15, 20, 25]
_.range(0, -10, -1);
=> [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
String.fromCharCode(..._.range('A'.charCodeAt(0), 'D'.charCodeAt(0) + 1));
=> "ABCD"
Old non es6 browsers without a library:
Array.apply(null, Array(5)).map(function (_, i) {return i;});
=> [0, 1, 2, 3, 4]
console.log([...Array(5).keys()]);
(ES6 credit to nils petersohn and other commenters)
Best Answer
noUiSlider offers an
updateOptions
method, which will keep all settings, save for any new ones you pass it. The documentation on updating is here.Starting from noUiSlider 8, you can do:
Disclosure: I'm the plugin author.