Fixed #43 - Implemented roString methods startsWith() and endsWith()

src/brsTypes/components/RoString.ts

@@ -46,6 +46,8 @@ export class RoString extends BrsComponent implements BrsValue, Comparable, Unbo
                 this.decodeUri,
                 this.encodeUriComponent,
                 this.decodeUriComponent,
+                this.startsWith,
+                this.endsWith,
                 this.isEmpty,
             ],
             ifToStr: [this.toStr],
@@ -478,6 +480,44 @@ export class RoString extends BrsComponent implements BrsValue, Comparable, Unbo
         },
     });
 
+    /** Checks whether the string starts with the substring specified in matchString, starting at the matchPos parameter (0-based character offset). */
+    private startsWith = new Callable("startsWith", {
+        signature: {
+            args: [
+                new StdlibArgument("matchString", ValueKind.String),
+                new StdlibArgument("position", ValueKind.Int32, BrsInvalid.Instance),
+            ],
+            returns: ValueKind.Boolean,
+        },
+        impl: (_: Interpreter, matchString: BrsString, position: Int32 | BrsInvalid) => {
+            if (position instanceof BrsInvalid) {
+                return BrsBoolean.from(this.intrinsic.value.startsWith(matchString.value));
+            }
+            return BrsBoolean.from(
+                this.intrinsic.value.startsWith(matchString.value, position.getValue())
+            );
+        },
+    });
+
+    /** Checks whether the string ends with the substring specified in matchString, starting at the position specified in the length parameter. */
+    private endsWith = new Callable("endsWith", {
+        signature: {
+            args: [
+                new StdlibArgument("matchString", ValueKind.String),
+                new StdlibArgument("position", ValueKind.Int32, BrsInvalid.Instance),
+            ],
+            returns: ValueKind.Boolean,
+        },
+        impl: (_: Interpreter, matchString: BrsString, position: Int32 | BrsInvalid) => {
+            if (position instanceof BrsInvalid) {
+                return BrsBoolean.from(this.intrinsic.value.endsWith(matchString.value));
+            }
+            return BrsBoolean.from(
+                this.intrinsic.value.endsWith(matchString.value, position.getValue())
+            );
+        },
+    });
+
     private toStr = new Callable("toStr", {
         signature: {
             args: [],

test/brsTypes/components/RoString.test.js

@@ -638,6 +638,41 @@ describe("RoString", () => {
             });
         });
 
+        describe("startsWith and endsWith", () => {
+            let s;
+            beforeEach(() => {
+                s = new RoString(new BrsString("Hello, World!"));
+            });
+
+            it("startsWith", () => {
+                let startsWith = s.getMethod("startsWith");
+                expect(startsWith).toBeInstanceOf(Callable);
+                expect(startsWith.call(interpreter, new BrsString("Hello"))).toEqual(
+                    BrsBoolean.True
+                );
+                expect(startsWith.call(interpreter, new BrsString("World"), new Int32(7))).toEqual(
+                    BrsBoolean.True
+                );
+                expect(
+                    startsWith.call(interpreter, new BrsString("Universe"), new Int32(0))
+                ).toEqual(BrsBoolean.False);
+            });
+
+            it("endsWith", () => {
+                let endsWith = s.getMethod("endsWith");
+                expect(endsWith).toBeInstanceOf(Callable);
+                expect(endsWith.call(interpreter, new BrsString("World!"))).toEqual(
+                    BrsBoolean.True
+                );
+                expect(endsWith.call(interpreter, new BrsString("Hello"), new Int32(5))).toEqual(
+                    BrsBoolean.True
+                );
+                expect(
+                    endsWith.call(interpreter, new BrsString("Universe!"), new Int32(0))
+                ).toEqual(BrsBoolean.False);
+            });
+        });
+
         describe("isEmpty", () => {
             it("check if empty string is empty", () => {
                 let s = new RoString(new BrsString(""));

test/e2e/BrsComponents.test.js

@@ -276,6 +276,10 @@ describe("end to end brightscript functions", () => {
             "🐶", // uri-encoded dog emoji, decoded
             "true", // isEmpty for empty string
             "false", // isEmpty for filled string
+            "true", // startsWith no position
+            "true", // startsWith with position
+            "true", // endsWith no position
+            "true", // endsWith with position
         ]);
     });
 

test/e2e/resources/components/roString.brs

@@ -28,4 +28,9 @@ sub main()
     print "%F0%9F%90%B6".decodeUriComponent() ' => 🐶
     print "".isEmpty() ' => true
     print "<3".isEmpty() ' => false
+
+    print "1234567890".startsWith("123") ' => true
+    print "1234567890".endsWith("890") ' => true
+    print "1234567890".startsWith("567", 4) ' => true
+    print "1234567890".endsWith("567", 7) ' => true
 end sub