LibJS: Add isFinite()

Author: https://github.com/linusg
Commit: 7540203ae8
Pull-request: https://github.com/SerenityOS/serenity/pull/1923

Libraries/LibJS/Tests/isFinite.js

@@ -0,0 +1,28 @@
+load("test-common.js");
+
+try {
+    assert(isFinite.length === 1);
+
+    assert(isFinite(0) === true);
+    assert(isFinite(42) === true);
+    assert(isFinite("") === true);
+    assert(isFinite("0") === true);
+    assert(isFinite("42") === true);
+    assert(isFinite(true) === true);
+    assert(isFinite(false) === true);
+    assert(isFinite(null) === true);
+    assert(isFinite([]) === true);
+
+    assert(isFinite() === false);
+    assert(isFinite(NaN) === false);
+    assert(isFinite(undefined) === false);
+    assert(isFinite(Infinity) === false);
+    assert(isFinite(-Infinity) === false);
+    assert(isFinite("foo") === false);
+    assert(isFinite({}) === false);
+    assert(isFinite([1, 2, 3]) === false);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e.message);
+}