27 Oct 2016

Tail call and optimization in ES6

As we know, if function calls himself, it is called recursion. However, recursion needs to take O(n) stacks in memory, which may cause stack overflow. For example,

function factorial(n) {
  if (n === 1) return 1;
  return n * factorial(n - 1);
}
factorial(5) // 120

If the recursion is the last step of the function, it is called tail call. It only takes O(1) stack in memory, so it will not cause stack overflow. The factorial function can be rewritten like this:

function factorial(n,total=1){
  if(n <= 1) return total;
  return factorial(n-1,total * n);
}
factorial(5) // 120

If a function is written in ES6 ‘use strict’ format, it will be optimized automatically. For the optimization detail, please refer to the ES6 docs

For further reading, please see this Reference

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