Addition of forEach() (#268)

* Addition of forEach()
* fixing LLDB launcher for windows (it needs .exe to work for windows)

.vscode/launch.json

@@ -8,13 +8,18 @@
       "type": "lldb",
       "request": "launch",
       "name": "Launch",
+      "windows": {
+        "program": "${workspaceFolder}/target/debug/boa_cli.exe"
+      },
       "program": "${workspaceFolder}/target/debug/boa_cli",
+      "args": ["${workspaceFolder}/tests/js/test.js"],
       "sourceLanguages": ["rust"]
     },
     {
       "name": "(Windows) Launch",
       "type": "cppvsdbg",
       "request": "launch",
+      "args": ["${workspaceFolder}/tests/js/test.js"],
       "program": "${workspaceFolder}/target/debug/boa_cli.exe",
       "cwd": "${workspaceFolder}",
       "sourceFileMap": {

.vscode/tasks.json

@@ -12,6 +12,9 @@
       "group": {
         "kind": "build",
         "isDefault": true
+      },
+      "presentation": {
+        "clear": true
       }
     },
     {
@@ -23,6 +26,9 @@
       "group": {
         "kind": "test",
         "isDefault": true
+      },
+      "presentation": {
+        "clear": true
       }
     }
   ]

boa/src/builtins/array/mod.rs

@@ -206,6 +206,33 @@ pub fn pop(this: &Value, _: &[Value], _: &mut Interpreter) -> ResultValue {
     Ok(pop_value)
 }
 
+/// Array.prototype.forEach ( callbackFn [ , thisArg ] )
+///
+/// This method executes the provided callback function for each element in the array.
+/// <https://tc39.es/ecma262/#sec-array.prototype.foreach>
+pub fn for_each(this: &Value, args: &[Value], interpreter: &mut Interpreter) -> ResultValue {
+    if args.is_empty() {
+        return Err(to_value(
+            "Missing argument for Array.prototype.forEach".to_string(),
+        ));
+    }
+
+    let callback_arg = args.get(0).expect("Could not get `callbackFn` argument.");
+    let this_arg = args.get(1).cloned().unwrap_or_else(undefined);
+
+    let length: i32 =
+        from_value(this.get_field_slice("length")).expect("Could not get `length` property.");
+
+    for i in 0..length {
+        let element = this.get_field_slice(&i.to_string());
+        let arguments = vec![element.clone(), to_value(i), this.clone()];
+
+        interpreter.call(callback_arg, &this_arg, arguments)?;
+    }
+
+    Ok(Gc::new(ValueData::Undefined))
+}
+
 /// Array.prototype.join ( separator )
 ///
 /// The elements of the array are converted to Strings, and these Strings are
@@ -732,7 +759,7 @@ pub fn create_constructor(global: &Value) -> Value {
     make_builtin_fn!(includes_value, named "includes", with length 1, of array_prototype);
     make_builtin_fn!(map, named "map", with length 1, of array_prototype);
     make_builtin_fn!(fill, named "fill", with length 1, of array_prototype);
-
+    make_builtin_fn!(for_each, named "forEach", with length 1, of array_prototype);
     make_builtin_fn!(pop, named "pop", of array_prototype);
     make_builtin_fn!(join, named "join", with length 1, of array_prototype);
     make_builtin_fn!(to_string, named "toString", of array_prototype);

boa/src/builtins/array/tests.rs

@@ -631,3 +631,47 @@ fn slice() {
     assert_eq!(forward(&mut engine, "many2.length"), "1");
     assert_eq!(forward(&mut engine, "many3.length"), "0");
 }
+
+#[test]
+fn for_each() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let init = r#"
+        var a = [2, 3, 4, 5];
+        var sum = 0;
+        var indexSum = 0;
+        var listLengthSum = 0;
+        function callingCallback(item, index, list) {
+            sum += item;
+            indexSum += index;
+            listLengthSum += list.length;
+        }
+        a.forEach(callingCallback);
+        "#;
+    forward(&mut engine, init);
+
+    assert_eq!(forward(&mut engine, "sum"), "14");
+    assert_eq!(forward(&mut engine, "indexSum"), "6");
+    assert_eq!(forward(&mut engine, "listLengthSum"), "16");
+}
+
+#[test]
+fn for_each_push_value() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let init = r#"
+        var a = [1, 2, 3, 4];
+        function callingCallback(item, index, list) {
+            list.push(item * 2);
+        }
+        a.forEach(callingCallback);
+        "#;
+    forward(&mut engine, init);
+
+    // [ 1, 2, 3, 4, 2, 4, 6, 8 ]
+    assert_eq!(forward(&mut engine, "a.length"), "8");
+    assert_eq!(forward(&mut engine, "a[4]"), "2");
+    assert_eq!(forward(&mut engine, "a[5]"), "4");
+    assert_eq!(forward(&mut engine, "a[6]"), "6");
+    assert_eq!(forward(&mut engine, "a[7]"), "8");
+}