Subnet Mask Conversion

This is a helper function to convert a subnet mask written as an IPv4 address to its equivalent suffix.

function subnetSuffix(mask) {
    if (mask) {
        return mask
            .split(".")                         // ["255", "255", "255", "0"]
            .map(i => (i >>> 0).toString(2))    // ["11111111", "11111111", "11111111", "0"]
            .join("")                           // "1111111111111111111111110"
            .replace(/0/g, "")                   // "111111111111111111111111"
            .length                             // 24
    }
    return 0;
}

subnetSuffix("255.255.255.0"); // 24

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