Group selector of Master styles

master-group.js

// Author: SerKo (https://github.com/serkodev)

function group(cls, sel) {
    return function parse(cls, sel) {
        if (typeof cls == "string") {
            return cls.split(/\s/).reduce((a, cur) => cur ? a.concat(cur + sel) : a, []);
        } else if (typeof cls == "object") {
            return cls.reduce((a, cur) => a.concat(...parse(cur, sel)), []);
        } else return [];
    }(cls, sel || "").join(" ");
}

group("f:1 m:2 p:3", "@xm");
// f:1@xm m:2@xm p:3@xm

group(["f:1", "m:2", "p:3"], "@xm");
// f:1@xm m:2@xm p:3@xm

group(["f:1 m:2", "p:3"], "@xm");
// f:1@xm m:2@xm p:3@xm

group([`
f:1
m:2
`,
    "p:3"],
    "@xm");
// f:1@xm m:2@xm p:3@xm