Leetcode 547 - friend circle - JavaScript code to study.

Leetcode547_friendCircles.js

/**
 * @param {number[][]} M
 * @return {number}
 */

var findCircleNum = function(M) {
    let numCircles = 0
    const visited = new Set ()
    M.forEach ((row, i) => {
        if (visited.has(i)) return
        numCircles++
        const queue = row.map((x, i) => x ? i : -1) . filter ((x) => x > -1)
        while (queue.length > 0) {
            const f = queue.pop ()
            if (!visited.has(f)) {
                visited.add (f)
                queue.push(... M[f].map((x, i) => x ? i : -1) . filter ((x) => x > -1))
            }
        }
    })
    return numCircles
};