How can I add a random number method in liquid that can called multiple times? - jekyll

Question

How can I add a random number in my liquid template files?
Is there something similar to PHP's rand()?
I have seen this used before, but if the variable is called in other places it displays the same number and is not randomized, even if multiple variables are created.
{% assign min = 65 %}
{% assign max = 80 %}
{% assign diff = max | minus: min %}
{% assign randomNumber = "now" | date: "%N" | modulo: diff | plus: min %}
This is how I am trying to accomplish it now:
<div class="contentDoubleWideWrap">
<div class="contentDoubleWideWrap">
{% assign min = 50 %}
{% assign max = 1000000 %}
{% assign diff = max | minus: min %}
{% assign randomNumber = site.time | date: "%s" | modulo: diff | plus: min %}
<div id="div-gpt-ad-1553024073723-{{ randomNumber }}" data-ad="div-gpt-ad-1553024073723-0" class="tmsads adContentDouble"></div>
</div>
<div class="contentDoubleWideWrap">
{% assign min2 = 50 %}
{% assign max2 = 1000000 %}
{% assign diff2 = max2 | minus: min2 %}
{% assign randomNumber2 = site.time | date: "%s" | modulo: diff2 | plus: min2 %}
<div id="div-gpt-ad-1553024121524-{{ randomNumber2 }}" data-ad="div-gpt-ad-1553024121524-0" class="tmsads adContentDouble"></div>
</div>
</div>

Answer 1

What you could do, it to define a prng, for example a linear congruential random number generator.
This works the following way:
you need a random seed (this can be date: "%N"),
you need the parameters of the rng: m, a, c
you need to specify the index into the generated pseudorandom series.
A good set of parameters:
m=2^31
a=1103515245
c=12345
This is used by GCC rand, see here for the link:
https://en.wikipedia.org/wiki/Linear_congruential_generator
the random number is created by (in pseudo code):
let x=seed
loop index times:
x=(a*x+c)%m
In this setting the random number you get from the generator can be further conditioned by the max, min, module parameters like you already did this for the date.
The only difference would be to use x instead of assign randomNumber = site.time | date: "%s"
You have almost everything in your code to do this. If you only need a few random numbers I would most probably simply unroll the loop in the pseudocode. Does that work for you?
Let me show how to implement the example you gave above:
<div class="contentDoubleWideWrap">
<div class="contentDoubleWideWrap">
{% assign min = 50 %}
{% assign max = 1000000 %}
{% assign diff = max | minus: min %}
{% assign seed = site.time | date: "%N" %}
{% assign randomNumber1 = seed | modulo: diff | plus: min %}
<div id="div-gpt-ad-1553024073723-{{ randomNumber1 }}" data-ad="div-gpt-ad-1553024073723-0" class="tmsads adContentDouble"></div>
</div>
<div class="contentDoubleWideWrap">
{% assign m = 2147483648 %}
{% assign a = 1103515245 %}
{% assign c = 12345 %}
{% assign min2 = 50 %}
{% assign max2 = 1000000 %}
{% assign diff2 = max2 | minus: min2 %}
{% assign randomNumber2 = seed | times: a | plus: c | modulo: m | modulo: diff2 | plus: min2 %}
<div id="div-gpt-ad-1553024121524-{{ randomNumber2 }}" data-ad="div-gpt-ad-1553024121524-0" class="tmsads adContentDouble"></div>
</div>
</div>
In this case x0 is seed and x1 the next state of the rng, you get randomNumber2 from that by modulo diff |plus: min2. To generate randomNumber3, you would repeate the a c and m filters one more time, like:
times: a | plus: c | modulo: m |times: a | plus: c | modulo: m
This can work if you only have a few random numbers to generate.
If you need more random numbers, you can use a loop instead to do the same thing.

Answer 2

The problem is that basically a static site is generated. What you could do is to move the random number generation to the client side, by using javascript. Does that work for you?

Answer 3

I bet it is possible via plugins, e.g. https://github.com/codecalm/jekyll-random
random_number(index, min=0, max=100, round=0)
Returns a number between min and max based on index. By default it returns a number between 0 and 100.
{% for i in (1..100) %}
{{ i }} - {{ forloop.index | random_number: 0, 10 }}
{% endfor %}
The code above returns random numbers like:
1 - 6
2 - 1
3 - 6
4 - 8
5 - 4
6 - 7
7 - 1
...