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how to separate the numbers in a string before the comma and push into an array

i have a string format like this:
var a=18,19,20
i want to seperate the numbers before comma and push them to my array which named temp:
while(a.indexOf(',')>-1){
var x=a.split(',');
temp.push(x);
}
but this is all came across my mind which does not work, the string length may vary from time to time,but the format is always the same(separated with a comma)unless i get a single number which does have comma

How to convert a string of big number to integer?

JavaScript converts all the big numbers into scientific notation.
eg: '90938498237058927340892374089' this string when converted to an integer will come out like this scientific notation '9.093849823705893e+28'.
How can I convert the data type from String to an Integer and avoiding the scientific notation?

In JS all the numbers are treated as floating-point so in end, they end up with precision you can use try BigInt('90938498237058927340892374089') which will give you exact number from string to number.
apart from this, you can also have a look here Javascript - parse string to long
this link might be helpful for you.

Try to use BigInt type:
BigInt('90938498237058927340892374089');
It returns BigInt number with 'n'-literal:
90938498237058927340892374089n

Can JSON values be numbers?

Can JSON values (not keys) be numbers, or do they HAVE to be strings only? So the following is valid.
{"number":"6"}
But is the following also valid?
{"number":6}

In JSON, 6 is the number six. "6" is a string containing the digit 6. So the answer to the question "Can json numbers be quoted?" is basically "no," because if you put them in quotes, they're not numbers anymore.
The only thing that needs to be between quotes is the property name (number).

It is valid JSON syntax. But beware that different programming languages will parse JSON differently..
https://www.freeformatter.com/json-validator.html

Json values can be
a string
a number
an object (JSON object)
an array
a boolean
null
See - https://www.w3schools.com/js/js_json_datatypes.asp

String to number to 2 decimal places

I have a string "215.00".
I want to convert this to a number and when I do parseInt("215.00") it returns 215 as a number. I want it to be as a number 215.00.
To try and do this I did parseFloat("215.00").toFixed(2);, however this also returns a string. I have found many answers on here, but they all convert the number to a string. Does anyone know how to fix this?
Please see my code attempt below:
var number = "215.00";
parseFloat(number).toFixed(2);
I want to get 215.00 as opposed to "215.00"

I will post here this as an Answer, for future purpose.
If you want to represent the zeros on the right hand-side, you need to represent it as a string. Because the numerical value of 215.00 it is in fact 215, therefore it will not keep the two decimal places.
The parseFloat method would work for a number such as "215.01", where it would parse it to the numerical value of 215.01.

Convert a byte for char A

In javascript I would like to convert this string: '0x7f, 0x88, 0x88, 0x88, 0x88, 0x7f'
to an object that look like this:
['B00000000','B01111111','B10001000','B10001000','B10001000','B10001000','B01111111','B00000000']
Both are displaying char A on a 8*8 Led matrix. How to do this in Javascript?

I won't write your code as you should really figure it out for yourself, but I will give you the (possible) process...
Split the string using .split function into an array
Loop through the
array and convert the Hex to int and store in a new array
Loop
through the new array and convert the ints to the B1111111 format
required. You can do this by starting with 128 and shifting right (or
halving) on each iteration. Compare to the int, if larger you get a 1
and subtract from the int. If not larger you get a 0. Add these 1s
and 0s onto a string and you have the binary representation. Add these strings into a new array, which will be your final result.
You can create an array with var arrayName = []; and then add to it with arrayName.push(someString);
Good luck!