Write a function that adds from two invocations in JavaScript

two_invocations.js

function addf(x) {
  return function(y) {
    return x + y;
  }
}

addf(3)(4)

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function addf(x) {
  var func = function(y) {
    return x + y;
  }
  return func;
}

addf(3)(4)

Nice explanation

thanks for explanation! :)