1 files changed, 45 insertions, 0 deletions
diff --git a/js/src/tests/non262/TypedArray/from_mapping.js b/js/src/tests/non262/TypedArray/from_mapping.js
new file mode 100644
index 0000000000..1c24815418
--- /dev/null
+++ b/js/src/tests/non262/TypedArray/from_mapping.js
@@ -0,0 +1,45 @@
+for (var constructor of anyTypedArrayConstructors) {
+    // If the mapfn argument to %TypedArray%.from is undefined, don't map.
+    assertDeepEq(constructor.from([3, 4, 5], undefined), new constructor([3, 4, 5]));
+    assertDeepEq(constructor.from([4, 5, 6], undefined, Math), new constructor([4, 5, 6]));
+
+    // mapfn is called with two arguments: value and index.
+    var log = [];
+    function f(...args) {
+        log.push(args);
+        return log.length;
+    }
+    assertDeepEq(constructor.from(['a', 'e', 'i', 'o', 'u'], f), new constructor([1, 2, 3, 4, 5]));
+    assertDeepEq(log, [['a', 0], ['e', 1], ['i', 2], ['o', 3], ['u', 4]]);
+
+    // If the object to be copied is non-iterable, mapfn is still called with two
+    // arguments.
+    log = [];
+    assertDeepEq(constructor.from({0: "zero", 1: "one", length: 2}, f), new constructor([1, 2]));
+    assertDeepEq(log, [["zero", 0], ["one", 1]]);
+
+    // If the object to be copied is iterable and the constructor is not Array,
+    // mapfn is still called with two arguments.
+    log = [];
+    function C(...rest) {
+        return new constructor(...rest);
+    }
+    C.from = constructor.from;
+    var c = new C(2);
+    c[0] = 1;
+    c[1] = 2;
+    assertDeepEq(C.from(["zero", "one"], f), c);
+    assertDeepEq(log, [["zero", 0], ["one", 1]]);
+
+    // The mapfn is called even if the value to be mapped is undefined.
+    assertDeepEq(constructor.from([0, 1, , 3], String), new constructor(["0", "1", "undefined", "3"]));
+    var arraylike = {length: 4, "0": 0, "1": 1, "3": 3};
+    assertDeepEq(constructor.from(arraylike, String), new constructor(["0", "1", "undefined", "3"]));
+}
+
+// %TypedArray%.from(obj, map) is not exactly the same as %TypedArray%.from(obj).map(mapFn).
+assertDeepEq(Int8Array.from([150], v => v / 2), new Int8Array([75]));
+assertDeepEq(Int8Array.from([150]).map(v => v / 2), new Int8Array([-53]));
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);