<pre class="shiki github-dark shaku"><code>/** * @param {number} num */function sum(num) { const inner = function (nextNum) { return nextNum ? sum(num + nextNum) : num } inner.valueOf = function () { return num } return inner}</code></pre>

create a sum()

Create a sum(), which makes following possible const sum1 = sum(1)sum1(2) == 3 // truesum1(3) == 4 // truesum(1)(2)(3) == 6 // truesum(5)(-1)(2) == 6 …