Question

我正在尝试运行以下示例。它使用sanctuary.js。

const {create, env} = require('sanctuary');
const S = create({checkTypes: false, env: env});
const test = require('tape');

class Person {
  constructor(name){
    this.name = S.maybeToEither('')(S.toMaybe(name));
  }
};

const capitalize = (string) => string[0].toUpperCase() + string.substring(1);
const tigerify = (string) => `${string}, the tiger`;
const display = (string) => string.toString();

const tigerize = S.compose(capitalize)(tigerify);

test("Displaying a person", (assert) => {
  const personOne = new Person("tony");
  const actual = S.either(S.identity)(tigerize)(personOne.name);
  const expected = 'Tony, the tiger';

  assert.equal(actual, expected);
  assert.end();
});

test("Displaying an anonymous person", (assert) => {
  const personTwo = new Person(null);
  const actual = S.either(S.identity)(tigerize)(personTwo.name);
  const expected = '';

  assert.equal(actual, expected);
  assert.end();
});

第28行第48个字符出现以下错误：

TypeError: (intermediate value)(intermediate value)(intermediate value) is not a function

这是由以下行中的personTwo.name引起的：

const actual = S.either(S.identity)(tigerize)(personTwo.name);

我可以看到personTwo.name是Left。为什么这会触发错误而不是返回一个空字符串？

Answer 1

看起来我部分使用了过时的api。

将S.identity更改为S.I示例有效。

我应该将什么价值传递给Sanctuary.either（）？

1 个答案: