尾调用优化 (TCO) 在 Safari 中不起作用

Question

According to ES6 compatibility table , Safari has tail call optimization feature. Tried it and it fails just like any other browser. Am I missing something?

 function factorial(n, r = 1n) { return (n <= 1)? r: factorial(n - 1n, n * r) } console.log(factorial(36000n))

Safari output:

RangeError: Maximum call stack size exceeded.

Answer 1

You need to run your program in strict mode.

 "use strict"; function factorial(n, r = 1n) { return n <= 1n? r: factorial(n - 1n, n * r); } console.log(factorial(36000n).toString());

There are four conditions that need to be met in order for a function call to be considered a proper tail call.

• The calling function is in strict mode .
• The calling function is either a normal function or an arrow function.
• The calling function is not a generator function.
• The return value of the called function is returned by the calling function.

Source: ECMAScript 6 Proper Tail Calls in WebKit by Michael Saboff