simplify index tracking in toSpliced

Author: acutmore

polyfill.js

@@ -182,20 +182,21 @@
     }
 
     function doSplice({ src, target, actualStart, actualDeleteCount, values, newLen }) {
-        let k = 0;
-        while (k < actualStart) {
-            target[k] = src[k];
-            k++;
+        let i = 0;
+        while (i < actualStart) {
+            target[i] = src[i];
+            i++;
         }
         for (const E of values) {
-            target[k] = E;
-            k++;
+            target[i] = E;
+            i++;
         }
-        while (k < newLen) {
-            let from = k + actualDeleteCount - values.length;
-            let fromValue = src[from];
-            target[k] = fromValue;
-            k++;
+        let r = actualStart + actualDeleteCount;
+        while (i < newLen) {
+            let fromValue = src[r];
+            target[i] = fromValue;
+            i++;
+            r++;
         }
     }
 

spec.html

@@ -88,22 +88,24 @@ <h1>Array.prototype.toSpliced ( _start_, _deleteCount_, ..._items_ )</h1>
                     1. Let _newLen_ be _len_ + _insertCount_ - _actualDeleteCount_.
                     1. If _newLen_ &gt; 2<sup>53</sup> - 1, throw a *TypeError* exception.
                     1. Let _A_ be ? ArrayCreate(𝔽(_newLen_)).
-                    1. Let _k_ be 0.
+                    1. Let _i_ be 0.
+                    1. Let _r_ be _actualStart_ + _actualDeleteCount_.
                     1. Repeat, while _k_ &lt; _actualStart_,
-                        1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                        1. Let _kValue_ be ? Get(_O_, _Pk_).
-                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pk_, _kValue_).
-                        1. Set _k_ to _k_ + 1.
+                        1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                        1. Let _iValue_ be ? Get(_O_, _Pi_).
+                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pi_, _iValue_).
+                        1. Set _i_ to _i_ + 1.
                     1. For each element _E_ of _items_, do
-                        1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pk_, _E_).
-                        1. Set _k_ to _k_ + 1.
-                    1. Repeat, while _k_ &lt; _newLen_,
-                        1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                        1. Let _from_ be ! ToString(𝔽(_k_ + _actualDeleteCount_ - _insertCount_)).
+                        1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pi_, _E_).
+                        1. Set _i_ to _i_ + 1.
+                    1. Repeat, while _i_ &lt; _newLen_,
+                        1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                        1. Let _from_ be ! ToString(𝔽(_r_)).
                         1. Let _fromValue_ be ? Get(_O_, _from_).
-                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pk_, _fromValue_).
-                        1. Set _k_ to _k_ + 1.
+                        1. Perform ! CreateDataPropertyOrThrow(_A_, _Pi_, _fromValue_).
+                        1. Set _i_ to _i_ + 1.
+                        1. Set _r_ to _r_ + 1.
                     1. Return _A_.
                 </emu-alg>
             </emu-clause>
@@ -284,22 +286,24 @@ <h1>%TypedArray%.prototype.toSpliced ( _start_, _deleteCount_, ..._items_ )</h1>
                             1. Let _actualDeleteCount_ be the result of clamping _dc_ between 0 and _len_ - _actualStart_.
                         1. Let _newLen_ be _len_ + _insert_Count_ - _actualDeleteCount_.
                         1. Let _A_ be ? TypedArrayCreateSameType(_O_, &laquo; 𝔽(_newLen_) &raquo;).
-                        1. Let _k_ be 0.
-                        1. Repeat, while _k_ &lt; _actualStart_,
-                            1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                            1. Let _kValue_ be ! Get(_src_, _Pk_).
-                            1. Perform ! Set(_target_, _Pk_, _kValue_, *true*).
-                            1. Set _k_ to _k_ + 1.
+                        1. Let _i_ be 0.
+                        1. Let _r_ be _actualStart_ + _actualDeleteCount_.
+                        1. Repeat, while _i_ &lt; _actualStart_,
+                            1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                            1. Let _iValue_ be ! Get(_src_, _Pi_).
+                            1. Perform ! Set(_target_, _Pi_, _iValue_, *true*).
+                            1. Set _i_ to _i_ + 1.
                         1. For each element _E_ of _items_, do
-                            1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                            1. Perform ? Set(_A_, _Pk_, _E_, *true*).
-                            1. Set _k_ to _k_ + 1.
-                        1. Repeat, while _k_ &lt; _newLen_,
-                            1. Let _Pk_ be ! ToString(𝔽(_k_)).
-                            1. Let _from_ be ! ToString(𝔽(_k_ + _actualDeleteCount_ - _insertCount_)).
+                            1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                            1. Perform ? Set(_A_, _Pi_, _E_, *true*).
+                            1. Set _i_ to _i_ + 1.
+                        1. Repeat, while _r_ &lt; _newLen_,
+                            1. Let _Pi_ be ! ToString(𝔽(_i_)).
+                            1. Let _from_ be ! ToString(𝔽(_r_)).
                             1. Let _fromValue_ be ! Get(_O_, _from_).
-                            1. Perform ! Set(_A_, _Pk_, _fromValue_, *true*).
-                            1. Set _k_ to _k_ + 1.
+                            1. Perform ! Set(_A_, _Pi_, _fromValue_, *true*).
+                            1. Set _i_ to _i_ + 1.
+                            1. Set _r_ to _r_ + 1.
                         1. Return _A_.
                     </emu-alg>
                 </emu-clause>