ユークリッドの互除法

test.js

let a = 273
   ,b = 1001

function* foo() {
    while (true) {
        yield (a < b) ? [a, b - a] : [a - b, a]
    }
}

for ([a, b] of foo(a, b)) {
    console.log(a, b)
    if (a === b) {
        break;
    }
}