Retranslate the complete English edition from Simplified Chinese (#2010)

* Retranslate the complete English edition from Simplified Chinese

* Polish three English explanations after reader-focused review

en/codes/javascript/chapter_computational_complexity/recursion.js

@@ -6,11 +6,11 @@
 
 /* Recursion */
 function recur(n) {
-    // Termination condition
+    // Base case
     if (n === 1) return 1;
-    // Recurse: recursive call
+    // Recurse: make a recursive call
     const res = recur(n - 1);
-    // Return: return result
+    // Unwind: return the result
     return n + res;
 }
 
@@ -19,14 +19,14 @@ function forLoopRecur(n) {
     // Use an explicit stack to simulate the system call stack
     const stack = [];
     let res = 0;
-    // Recurse: recursive call
+    // Recurse: make a recursive call
     for (let i = n; i > 0; i--) {
-        // Simulate "recurse" with "push"
+        // Simulate recursive calls by pushing onto the stack
         stack.push(i);
     }
-    // Return: return result
+    // Unwind: return the result
     while (stack.length) {
-        // Simulate "return" with "pop"
+        // Simulate unwinding by popping from the stack
         res += stack.pop();
     }
     // res = 1+2+3+...+n
@@ -35,35 +35,35 @@ function forLoopRecur(n) {
 
 /* Tail recursion */
 function tailRecur(n, res) {
-    // Termination condition
+    // Base case
     if (n === 0) return res;
-    // Tail recursive call
+    // Tail-recursive call
     return tailRecur(n - 1, res + n);
 }
 
 /* Fibonacci sequence: recursion */
 function fib(n) {
-    // Termination condition f(1) = 0, f(2) = 1
+    // Base cases: f(1) = 0, f(2) = 1
     if (n === 1 || n === 2) return n - 1;
-    // Recursive call f(n) = f(n-1) + f(n-2)
+    // Recursive calls: f(n) = f(n-1) + f(n-2)
     const res = fib(n - 1) + fib(n - 2);
-    // Return result f(n)
+    // Return the result f(n)
     return res;
 }
 
-/* Driver Code */
+/* Driver code */
 const n = 5;
 let res;
 
 res = recur(n);
-console.log(`Recursion sum result res = ${res}`);
+console.log(`Sum from the recursive function: res = ${res}`);
 
 res = forLoopRecur(n);
-console.log(`Using iteration to simulate recursion sum result res = ${res}`);
+console.log(`Sum from simulating recursion with iteration: res = ${res}`);
 
 res = tailRecur(n, 0);
-console.log(`Tail recursion sum result res = ${res}`);
+console.log(`Sum from the tail-recursive function: res = ${res}`);
 
 res = fib(n);
-console.log(`The ${n}th Fibonacci number is ${res}`);
+console.log(`Fibonacci term ${n} is ${res}`);