Get intersection between two ranges in JavaScript

In JavaScript, finding the intersection between two numerical ranges involves determining the overlapping portion. A range is typically represented as an array with two elements: [start, end].

Understanding Range Intersection

The intersection of two ranges is the overlapping segment. For ranges [2, 5] and [4, 7], the intersection is [4, 5] because that's where they overlap.

const arr1 = [2, 5];
const arr2 = [4, 7];
console.log("Range 1:", arr1);
console.log("Range 2:", arr2);

Range 1: [ 2, 5 ]
Range 2: [ 4, 7 ]

Algorithm

To find the intersection, we need:

• Left boundary: Maximum of both starting points
• Right boundary: Minimum of both ending points

Example

const arr1 = [2, 5];
const arr2 = [4, 7];

const findRangeIntersection = (arr1 = [], arr2 = []) => {
    const [el11, el12] = arr1;
    const [el21, el22] = arr2;
    const leftLimit = Math.max(el11, el21);
    const rightLimit = Math.min(el12, el22);
    return [leftLimit, rightLimit];
};

console.log(findRangeIntersection(arr1, arr2));

[ 4, 5 ]

Handling Edge Cases

Sometimes ranges don't overlap. We should check if the intersection is valid:

const findValidIntersection = (range1, range2) => {
    const [start1, end1] = range1;
    const [start2, end2] = range2;
    
    const leftLimit = Math.max(start1, start2);
    const rightLimit = Math.min(end1, end2);
    
    // Check if intersection is valid
    if (leftLimit 

Overlapping: [ 4, 5 ]
Non-overlapping: null


Multiple Examples

const testCases = [
    [[1, 5], [3, 7]],   // [3, 5]
    [[0, 2], [1, 4]],   // [1, 2]
    [[5, 10], [2, 6]],  // [5, 6]
    [[1, 3], [4, 6]]    // No overlap
];

testCases.forEach(([range1, range2], index) => {
    const result = findValidIntersection(range1, range2);
    console.log(`Test ${index + 1}: [${range1}] ? [${range2}] = ${result ? `[${result}]` : 'No intersection'}`);
});


Test 1: [1,5] ? [3,7] = [3,5]
Test 2: [0,2] ? [1,4] = [1,2]
Test 3: [5,10] ? [2,6] = [5,6]
Test 4: [1,3] ? [4,6] = No intersection


Conclusion

Finding range intersection involves taking the maximum of start values and minimum of end values. Always validate that the resulting range is valid (left ? right) to handle non-overlapping cases.