Function mapper

deps/v8/test/mjsunit/es6/typedarray-from.js:99–101

(value, index)

  // Use a map function that returns non-numbers.
  function mapper(value, index) {
    return String.fromCharCode(value);
  }
  var d = defaultValue(constructor);
  assertArrayLikeEquals(
      constructor.from([72, 69, 89], mapper), [d, d, d], constructor);