Compare 2 variables with comma separated values in JavaScript

Question

I have 2 variables say a=1,2,3,4 and b=1,2 , I want to compare these 2 variables and form a new variable with common values, please help me

`a=1,2,3,4` is just the same as `a=4`. See [What does a comma do in JavaScript expressions?](https://stackoverflow.com/q/3561043) and [Comma operator returns first value instead of second in argument list?](https://stackoverflow.com/q/5580596) — VLAZ, May 06 '21 at 15:37
[How much research effort is expected of Stack Overflow users?](https://meta.stackoverflow.com/questions/261592/how-much-research-effort-is-expected-of-stack-overflow-users), [How do I ask a good question?](https://stackoverflow.com/help/how-to-ask) — Andreas, May 06 '21 at 15:37

score 0 · Accepted Answer · answered May 06 '21 at 15:40

Assuming you meant:

a="1,2,3,4"
b="1,2"

You could break those comma delimited values into arrays and then get the intersections of the arrays. Here's an example:

const ArrayA = a.split(",");
const ArrayB = b.split(",");

const intersection = ArrayA.filter(value => ArrayB.includes(value));
const commonCSV = intersection.join(",");

score 0 · Answer 2 · answered May 06 '21 at 15:55

var a = [1, 2, 3, 4];
var b = [1, 2];

// Take unqiue values from a and concat with unique values from b
const occurrenceMap = [...new Set(a)].concat([...new Set(b)]).reduce((map, el) => {
  map.set(el, map.get(el) ? map.get(el) + 1 : 1);

  return map;
}, new Map());

const common = [];

// Iterate over the map entries and keep only the ones that occur more than once - these would be the intersection of the 2 arrays.
for (entry of occurrenceMap) {
  const [key, val] = entry;

  if (val > 1) {
    common.push(key);
  }
}


console.log(common);

Compare 2 variables with comma separated values in JavaScript

2 Answers2