I have 2 arrays lets say:
A = [1,2,3,4,5] and B = [1,2,3,6,7]
and I'd like to perform the following 'set calculations':
C = (A ∩ B)
D = A - (A ∩ B)
E = B - (A ∩ B)
Essentially:
C = [1,2,3]
D = [4,5]
E = [6,7]
Is there a smart way to do this or am I going to have to cross check each array member with loops and ifs? I cannot use an external library (like math.js or w/e).
Thanks in advance.
filter() can at least hide the loops for you:
A = [1,2,3,4,5];
B = [1,2,3,6,7];
C = intersection(A, B);
D = arrayDiff(A, C);
E = arrayDiff(B, C);
console.log(JSON.stringify(C));
console.log(JSON.stringify(D));
console.log(JSON.stringify(E));
function intersection(a, b) {
return a.filter(
function(el) {
return b.indexOf(el) >= 0;
}
);
}
function arrayDiff(a, b) {
return a.filter(
function(el) {
return b.indexOf(el) < 0;
}
);
}
As of ES6, Javascript has an inbuilt set object, which offers neat ways to do the above operations.
var intersection = (setA, setB) => new Set([...setA].filter(x => setB.has(x)));
var difference = (setA, setB) => new Set([...setA].filter(x => !setB.has(x)));
A = new Set([1,2,3,4,5]);
B = new Set([1,2,3,6,7]);
// A ∩ B = ([1,2,3])
console.log(intersection(A, B));
// A \ B = ([4,5])
console.log(difference(A, B));
// B \ A = ([6,7])
console.log(difference(B, A));
