LibJS: Add JSON.stringify

Libraries/LibJS/Tests/JSON.stringify-space.js

@@ -0,0 +1,51 @@
+load("test-common.js");
+
+try {
+    let o = {
+        foo: 1,
+        bar: "baz",
+        qux: {
+            get x() { return 10; },
+            y() { return 20; },
+            arr: [1, 2, 3],
+        }
+    };
+
+    let string = JSON.stringify(o, null, 4);
+    let expected =
+`{
+    "foo": 1,
+    "bar": "baz",
+    "qux": {
+        "x": 10,
+        "arr": [
+            1,
+            2,
+            3
+        ]
+    }
+}`;
+
+    assert(string === expected);
+
+    string = JSON.stringify(o, null, "abcd");
+    expected =
+`{
+abcd"foo": 1,
+abcd"bar": "baz",
+abcd"qux": {
+abcdabcd"x": 10,
+abcdabcd"arr": [
+abcdabcdabcd1,
+abcdabcdabcd2,
+abcdabcdabcd3
+abcdabcd]
+abcd}
+}`;
+
+    assert(string === expected);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}