added support for char_code_at()

.vscode/tasks.json

@@ -1,11 +1,11 @@
 {
-    // See https://go.microsoft.com/fwlink/?LinkId=733558
+    // See https://go.microsoft.com/fwlink/?LinkId=733558 
     // for the documentation about the tasks.json format
     "version": "2.0.0",
     "tasks": [
         {
-            "type": "cargo",
-            "label": "cargo run",
+            "type": "process",
+            "label": "Cargo Run",
             "command": "cargo",
             "args": [
                 "run"
@@ -17,21 +17,6 @@
                 "kind": "build",
                 "isDefault": true
             }
-        },
-        {
-            "type": "cargo",
-            "label": "cargo Test",
-            "command": "cargo",
-            "args": [
-                "test"
-            ],
-            "problemMatcher": [
-                "$rustc"
-            ],
-            "group": {
-                "kind": "test",
-                "isDefault": true
-            }
         }
     ]
 }

src/lib/js/string.rs

@@ -2,6 +2,7 @@ use crate::js::function::NativeFunctionData;
 use crate::js::object::{Property, PROTOTYPE};
 use crate::js::value::{from_value, to_value, ResultValue, Value, ValueData};
 use gc::Gc;
+use std::f64::NAN;
 
 /// Create new string
 /// https://searchfox.org/mozilla-central/source/js/src/vm/StringObject.h#19
@@ -30,10 +31,10 @@ pub fn to_string(this: Value, _: Value, _: Vec<Value>) -> ResultValue {
     Ok(to_value(format!("{}", primitive_val).to_string()))
 }
 
-// Get the character at the supplied index
-// https://tc39.github.io/ecma262/#sec-string.prototype.charat
+/// Get the character at the supplied index
+/// https://tc39.github.io/ecma262/#sec-string.prototype.charat
 pub fn char_at(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
-    //          ^^ represents instance       ^^ represents arguments (we only care about the first one in this case)
+    //         ^^ represents instance  ^^ represents arguments (we only care about the first one in this case)
     // First we get it the actual string a private field stored on the object only the engine has access to.
     // Then we convert it into a Rust String by wrapping it in from_value
     let primitive_val: String =
@@ -45,13 +46,37 @@ pub fn char_at(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
     let length = primitive_val.chars().count();
 
     // We should return an empty string is pos is out of range
-    if pos > length || pos < 0 as usize {
+    if pos >= length || pos < 0 as usize {
         return Ok(to_value::<String>(String::new()));
     }
 
     Ok(to_value::<char>(primitive_val.chars().nth(pos).unwrap()))
 }
 
+/// Get the character (UTF 16) of string
+/// https://tc39.github.io/ecma262/#sec-string.prototype.charcodeat
+pub fn char_code_at(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
+    //              ^^ represents instance  ^^ represents arguments (we only care about the first one in this case)
+    // First we get it the actual string a private field stored on the object only the engine has access to.
+    // Then we convert it into a Rust String by wrapping it in from_value
+    let primitive_val: String =
+        from_value(this.get_private_field(String::from("PrimitiveValue"))).unwrap();
+
+    // Calling .len() on a string would give the wrong result, as they are bytes not the number of unicode code points
+    // Note that this is an O(N) operation (because UTF-8 is complex) while getting the number of bytes is an O(1) operation.
+    let length = primitive_val.chars().count();
+    let pos = from_value(args[0].clone()).unwrap();
+
+    if pos >= length || pos < 0 as usize {
+        return Ok(to_value(NAN));
+    }
+
+    let utf16_val = primitive_val.encode_utf16().nth(pos).unwrap();
+    // If there is no element at that index, the result is NaN
+    // TODO: We currently don't have NaN
+    Ok(to_value(utf16_val as f64))
+}
+
 /// Create a new `String` object
 pub fn _create(global: Value) -> Value {
     let string = to_value(make_string as NativeFunctionData);
@@ -66,6 +91,7 @@ pub fn _create(global: Value) -> Value {
     };
     proto.set_prop_slice("length", prop);
     proto.set_field_slice("charAt", to_value(char_at as NativeFunctionData));
+    proto.set_field_slice("charCodeAt", to_value(char_code_at as NativeFunctionData));
     proto.set_field_slice("toString", to_value(to_string as NativeFunctionData));
     string.set_field_slice(PROTOTYPE, proto);
     string

tests/js/test.js

@@ -1,2 +1,2 @@
-var a = new String("test");
-a.charAt(9);
+var a = new String("ABC");
+a.charCodeAt(-1);