From f8b1997cc495f514405317ce6fce090e1b8d81e1 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:08:25 -0400
Subject: [PATCH 01/17] Initial commit of comments and function

---
 boa/src/builtins/array/mod.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index e79683cb1af..2c71a3b1af7 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -487,6 +487,20 @@ impl Array {
         Ok(a.into())
     }
 
+    ///'Array.prototype.at(index)'
+    ///
+    /// When at method is called with desired index, it returns the value at given
+    /// index. If index is invalid, the at method returns undefined.
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-array.prototype.at
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at
+    pub(crate) fn at(this: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
+        //let O be ? ToObject(this value)
+        let obj = this.to_object(context)?;
+
+        Ok()
+    }
+
     /// `Array.prototype.concat(...arguments)`
     ///
     /// When the concat method is called with zero or more arguments, it returns an

From b2a835f2ed13642933d514990d74709fecf1677d Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:14:36 -0400
Subject: [PATCH 02/17] Adding ECMAScript step comment outlines

---
 boa/src/builtins/array/mod.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 2c71a3b1af7..73994d2cf24 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -492,12 +492,23 @@ impl Array {
     /// When at method is called with desired index, it returns the value at given
     /// index. If index is invalid, the at method returns undefined.
     ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
     /// [spec]: https://tc39.es/ecma262/#sec-array.prototype.at
     /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at
     pub(crate) fn at(this: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
-        //let O be ? ToObject(this value)
+        //1. let O be ? ToObject(this value)
         let obj = this.to_object(context)?;
-
+        //2. let len be ? LengthOfArrayLike(O)
+        //3. let relativeIndex be ? ToIntegerOrInfinity(index)
+        //4. if relativeIndex >= 0, then
+        //a. let k be relativeIndex
+        //5. Else,
+        //a. let k be len + relativeIndex
+        //6. if k <0> or k >= len, return undefined
+        //7. Return ? Get(O, !ToString(𝔽(k)))
         Ok()
     }
 

From 270508db3676a1bfd085e83a199685e950446dc7 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:33:27 -0400
Subject: [PATCH 03/17] code written for all steps - comments reformatted

---
 boa/src/builtins/array/mod.rs | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 73994d2cf24..e6bc3a46d7c 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -502,14 +502,27 @@ impl Array {
         //1. let O be ? ToObject(this value)
         let obj = this.to_object(context)?;
         //2. let len be ? LengthOfArrayLike(O)
+        let len = obj.length_of_array_like(context)?;
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
-        //4. if relativeIndex >= 0, then
-        //a. let k be relativeIndex
-        //5. Else,
-        //a. let k be len + relativeIndex
-        //6. if k <0> or k >= len, return undefined
-        //7. Return ? Get(O, !ToString(𝔽(k)))
-        Ok()
+        let relativeIndex = args.get(0).unwrap().to_integer_or_infinity(context)?;
+        let k = match relativeIndex {
+            //4. if relativeIndex >= 0, then let k be relativeIndex
+            IntegerOrInfinity::Integer(i) if i >= 0 => i,
+            //5. Else, let k be len + relativeIndex
+            IntegerOrInfinity::Integer(i) => len + i,
+            //handle most likely impossible case of
+            //IntegerOrInfinity::NegativeInfinity | IntegerOrInfinity::PositiveInfinity
+            //by setting to len which will return undefined
+            _ => len,
+        };
+        //6. if k < 0  or k >= len,
+        if k < 0 || k >= len {
+            //return undefined
+            Ok(JsValue::undefined())
+        } else {
+            //7. Return ? Get(O, !ToString(𝔽(k)))
+            obj.get(k, context)?
+        }
     }
 
     /// `Array.prototype.concat(...arguments)`

From 7464179d92575ff9af5f305f92dbbdded83a9dda Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:36:58 -0400
Subject: [PATCH 04/17] Added extra | to comment

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index e6bc3a46d7c..1c7d341d202 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -511,7 +511,7 @@ impl Array {
             //5. Else, let k be len + relativeIndex
             IntegerOrInfinity::Integer(i) => len + i,
             //handle most likely impossible case of
-            //IntegerOrInfinity::NegativeInfinity | IntegerOrInfinity::PositiveInfinity
+            //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
             //by setting to len which will return undefined
             _ => len,
         };

From be10c9fb0d25381fa43a7bd662c01b22a5e53191 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:39:39 -0400
Subject: [PATCH 05/17] Cleaning up comments on match _ arm

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 1c7d341d202..7a8a69bfcb8 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -512,7 +512,7 @@ impl Array {
             IntegerOrInfinity::Integer(i) => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
-            //by setting to len which will return undefined
+            //by setting k to len which will return undefined below
             _ => len,
         };
         //6. if k < 0  or k >= len,

From db5725ac2752b4cccaf3781166ca75d7f0e8a9e3 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:45:39 -0400
Subject: [PATCH 06/17] Updated top level comment block

---
 boa/src/builtins/array/mod.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 7a8a69bfcb8..a4feaa6d7d3 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -489,8 +489,9 @@ impl Array {
 
     ///'Array.prototype.at(index)'
     ///
-    /// When at method is called with desired index, it returns the value at given
-    /// index. If index is invalid, the at method returns undefined.
+    /// When at method takes desired integer as index and returns the value at given
+    /// index. Negative integer counts backwards. If index is invalid, the at method
+    /// returns undefined.
     ///
     /// More information:
     ///  - [ECMAScript reference][spec]

From 07aebb95a8ed51e290e6ab87011e961a920d176c Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Fri, 1 Oct 2021 22:50:02 -0400
Subject: [PATCH 07/17] Added at method to constructor's prototype at line 89

---
 boa/src/builtins/array/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index a4feaa6d7d3..b0eeb3d019d 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -86,6 +86,7 @@ impl BuiltIn for Array {
             values_function,
             Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE,
         )
+        .method(Self::at, "at", 1)
         .method(Self::concat, "concat", 1)
         .method(Self::push, "push", 1)
         .method(Self::index_of, "indexOf", 1)

From 138a755aa1fc520bbf538395bdc11ce4e9fa026a Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 11:13:15 -0400
Subject: [PATCH 08/17] Fixing some errors involving len being usize and return
 type

---
 boa/src/builtins/array/mod.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index b0eeb3d019d..b4c2ace881a 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -504,7 +504,7 @@ impl Array {
         //1. let O be ? ToObject(this value)
         let obj = this.to_object(context)?;
         //2. let len be ? LengthOfArrayLike(O)
-        let len = obj.length_of_array_like(context)?;
+        let len = obj.length_of_array_like(context)? as i64;
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
         let relativeIndex = args.get(0).unwrap().to_integer_or_infinity(context)?;
         let k = match relativeIndex {
@@ -523,7 +523,7 @@ impl Array {
             Ok(JsValue::undefined())
         } else {
             //7. Return ? Get(O, !ToString(𝔽(k)))
-            obj.get(k, context)?
+            obj.get(k, context)
         }
     }
 

From f9bb0ac983c103dec672ad12697340638c1c8dd3 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 11:14:50 -0400
Subject: [PATCH 09/17] changed relativeIndex to relative_index for rust

---
 boa/src/builtins/array/mod.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index b4c2ace881a..9c04c73f6f4 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -506,8 +506,8 @@ impl Array {
         //2. let len be ? LengthOfArrayLike(O)
         let len = obj.length_of_array_like(context)? as i64;
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
-        let relativeIndex = args.get(0).unwrap().to_integer_or_infinity(context)?;
-        let k = match relativeIndex {
+        let relative_index = args.get(0).unwrap().to_integer_or_infinity(context)?;
+        let k = match relative_index {
             //4. if relativeIndex >= 0, then let k be relativeIndex
             IntegerOrInfinity::Integer(i) if i >= 0 => i,
             //5. Else, let k be len + relativeIndex

From 57b51ce89df625780b662abfd8da770473983e51 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 12:40:50 -0400
Subject: [PATCH 10/17] return 0 index by default in the case of no args given

---
 boa/src/builtins/array/mod.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 9c04c73f6f4..05e3515340a 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -505,8 +505,10 @@ impl Array {
         let obj = this.to_object(context)?;
         //2. let len be ? LengthOfArrayLike(O)
         let len = obj.length_of_array_like(context)? as i64;
+        //handle unwrap() panicking on no input -> returns 0 index by default on at()
+        let arg_index = args.get(0).unwrap_or(&JsValue::new(0)).clone();
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
-        let relative_index = args.get(0).unwrap().to_integer_or_infinity(context)?;
+        let relative_index = arg_index.to_integer_or_infinity(context)?;
         let k = match relative_index {
             //4. if relativeIndex >= 0, then let k be relativeIndex
             IntegerOrInfinity::Integer(i) if i >= 0 => i,

From 1a9c4a986e559dfcd99a3b0f07f97f468d1a76a8 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 12:49:46 -0400
Subject: [PATCH 11/17] fixed comment on change for better readability

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 05e3515340a..213c97727b1 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -505,7 +505,7 @@ impl Array {
         let obj = this.to_object(context)?;
         //2. let len be ? LengthOfArrayLike(O)
         let len = obj.length_of_array_like(context)? as i64;
-        //handle unwrap() panicking on no input -> returns 0 index by default on at()
+        //fetch provided index, defaults to 0 index by default on at()
         let arg_index = args.get(0).unwrap_or(&JsValue::new(0)).clone();
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
         let relative_index = arg_index.to_integer_or_infinity(context)?;

From 18e26e39f082be82d0c618d993ff0a9d90790dc3 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 12:59:50 -0400
Subject: [PATCH 12/17] made changes according to review feedback

---
 boa/src/builtins/array/mod.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 213c97727b1..6e340e7f782 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -490,9 +490,10 @@ impl Array {
 
     ///'Array.prototype.at(index)'
     ///
-    /// When at method takes desired integer as index and returns the value at given
-    /// index. Negative integer counts backwards. If index is invalid, the at method
-    /// returns undefined.
+    /// The at() method takes an integer value and returns the
+    /// item at that index, allowing for positive and negative
+    /// integers. Negative integers count back from the last
+    /// item in the array.
     ///
     /// More information:
     ///  - [ECMAScript reference][spec]
@@ -505,10 +506,8 @@ impl Array {
         let obj = this.to_object(context)?;
         //2. let len be ? LengthOfArrayLike(O)
         let len = obj.length_of_array_like(context)? as i64;
-        //fetch provided index, defaults to 0 index by default on at()
-        let arg_index = args.get(0).unwrap_or(&JsValue::new(0)).clone();
         //3. let relativeIndex be ? ToIntegerOrInfinity(index)
-        let relative_index = arg_index.to_integer_or_infinity(context)?;
+        let relative_index = args.get_or_undefined(0).to_integer_or_infinity(context)?;
         let k = match relative_index {
             //4. if relativeIndex >= 0, then let k be relativeIndex
             IntegerOrInfinity::Integer(i) if i >= 0 => i,
@@ -516,8 +515,8 @@ impl Array {
             IntegerOrInfinity::Integer(i) => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
-            //by setting k to len which will return undefined below
-            _ => len,
+            //by returning undefined
+            _ => return Ok(JsValue::undefined()),
         };
         //6. if k < 0  or k >= len,
         if k < 0 || k >= len {

From 224dc93fccc2658284955edf4a2c112812de7d0c Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 13:01:09 -0400
Subject: [PATCH 13/17] updated comment block lines for readability

---
 boa/src/builtins/array/mod.rs | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 6e340e7f782..945662c8f17 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -490,10 +490,9 @@ impl Array {
 
     ///'Array.prototype.at(index)'
     ///
-    /// The at() method takes an integer value and returns the
-    /// item at that index, allowing for positive and negative
-    /// integers. Negative integers count back from the last
-    /// item in the array.
+    /// The at() method takes an integer value and returns the item at that
+    /// index, allowing for positive and negative integers. Negative integers
+    /// count back from the last item in the array.
     ///
     /// More information:
     ///  - [ECMAScript reference][spec]

From e11bfc4122ecb14f97720e6b37d1174346145ce7 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 13:16:23 -0400
Subject: [PATCH 14/17] adding match guard update - removes need of step 6

---
 boa/src/builtins/array/mod.rs | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 945662c8f17..971b4a732d3 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -509,22 +509,20 @@ impl Array {
         let relative_index = args.get_or_undefined(0).to_integer_or_infinity(context)?;
         let k = match relative_index {
             //4. if relativeIndex >= 0, then let k be relativeIndex
-            IntegerOrInfinity::Integer(i) if i >= 0 => i,
+            //check if positive and if below length of array
+            IntegerOrInfinity::Integer(i) if i >= 0 && i < len => i,
             //5. Else, let k be len + relativeIndex
-            IntegerOrInfinity::Integer(i) => len + i,
+            //should be negative, so abs() and check if less than or equal to length of array
+            IntegerOrInfinity::Integer(i) if i.abs() <= len => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
             //by returning undefined
             _ => return Ok(JsValue::undefined()),
         };
         //6. if k < 0  or k >= len,
-        if k < 0 || k >= len {
-            //return undefined
-            Ok(JsValue::undefined())
-        } else {
-            //7. Return ? Get(O, !ToString(𝔽(k)))
-            obj.get(k, context)
-        }
+        //handled by the above match guards
+        //7. Return ? Get(O, !ToString(𝔽(k)))
+        obj.get(k, context)
     }
 
     /// `Array.prototype.concat(...arguments)`

From 753f517a6989b1e647f909fc77e7daa096b7f455 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 13:18:44 -0400
Subject: [PATCH 15/17] clean up comments on match guards

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 971b4a732d3..0076879267e 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -512,7 +512,7 @@ impl Array {
             //check if positive and if below length of array
             IntegerOrInfinity::Integer(i) if i >= 0 && i < len => i,
             //5. Else, let k be len + relativeIndex
-            //should be negative, so abs() and check if less than or equal to length of array
+            //integer should be negative, so abs() and check if less than or equal to length of array
             IntegerOrInfinity::Integer(i) if i.abs() <= len => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity

From 1acc870b290663876ae7259937400081a86d69e2 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 13:40:22 -0400
Subject: [PATCH 16/17] fixing potential match bug involving arg being len

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 0076879267e..798f79470b7 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -513,7 +513,7 @@ impl Array {
             IntegerOrInfinity::Integer(i) if i >= 0 && i < len => i,
             //5. Else, let k be len + relativeIndex
             //integer should be negative, so abs() and check if less than or equal to length of array
-            IntegerOrInfinity::Integer(i) if i.abs() <= len => len + i,
+            IntegerOrInfinity::Integer(i) if i.abs() <= len && i != len => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
             //by returning undefined

From 0a6d4ebbb91e4b90a56c2f0d97e63cfd093cf7a8 Mon Sep 17 00:00:00 2001
From: nekevss <46825870+nekevss@users.noreply.github.com>
Date: Sat, 2 Oct 2021 22:47:28 -0400
Subject: [PATCH 17/17] logic update to match guard on second arm for
 readability

---
 boa/src/builtins/array/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 798f79470b7..3807b00c2e2 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -513,7 +513,7 @@ impl Array {
             IntegerOrInfinity::Integer(i) if i >= 0 && i < len => i,
             //5. Else, let k be len + relativeIndex
             //integer should be negative, so abs() and check if less than or equal to length of array
-            IntegerOrInfinity::Integer(i) if i.abs() <= len && i != len => len + i,
+            IntegerOrInfinity::Integer(i) if i < 0 && i.abs() <= len => len + i,
             //handle most likely impossible case of
             //IntegerOrInfinity::NegativeInfinity || IntegerOrInfinity::PositiveInfinity
             //by returning undefined