LibJS: Add Array.prototype.map()

Author: https://github.com/linusg
Commit: f7df521073
Pull-request: https://github.com/SerenityOS/serenity/pull/1793

Libraries/LibJS/Tests/Array.prototype.map.js

@@ -0,0 +1,51 @@
+load("test-common.js");
+
+try {
+    assert(Array.prototype.map.length === 1);
+
+    try {
+        [].map();
+        assertNotReached();
+    } catch (e) {
+        assert(e.name === "TypeError");
+        assert(e.message === "Array.prototype.map() requires at least one argument");
+    }
+
+    try {
+        [].map(undefined);
+        assertNotReached();
+    } catch (e) {
+        assert(e.name === "TypeError");
+        assert(e.message === "undefined is not a function");
+    }
+
+    var callbackCalled = 0;
+    var callback = () => { callbackCalled++; };
+
+    assert([].map(callback).length === 0);
+    assert(callbackCalled === 0);
+
+    assert([1, 2, 3].map(callback).length === 3);
+    assert(callbackCalled === 3);
+
+    var results = [undefined, null, true, "foo", 42, {}].map((value, index) => "" + index + " -> " + value);
+    assert(results.length === 6);
+    assert(results[0] === "0 -> undefined");
+    assert(results[1] === "1 -> null");
+    assert(results[2] === "2 -> true");
+    assert(results[3] === "3 -> foo");
+    assert(results[4] === "4 -> 42");
+    assert(results[5] === "5 -> [object Object]");
+
+    var squaredNumbers = [0, 1, 2, 3, 4].map(x => x ** 2);
+    assert(squaredNumbers.length === 5);
+    assert(squaredNumbers[0] === 0);
+    assert(squaredNumbers[1] === 1);
+    assert(squaredNumbers[2] === 4);
+    assert(squaredNumbers[3] === 9);
+    assert(squaredNumbers[4] === 16);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}