ramda JS Concat的使用减少的值

Question

我有数据的阵列将被转换成一个字符串。我创建了功能做变换。我的问题是什么是写这个功能，使其更具可读性的最佳方式？我不想有多个if/else语句。

const data = [
    "hello",
    {name: "Bob"},
    "and",
    {name: "Fred"},
    "How are you guys today?",
]

const isString = R.is(String)
const isObject = R.is(Object)

const getName = R.prop('name')

const toPureString = R.reduce(
    (result, value) => {
        if (isString(value)) {
            return `${result}${value} `
        }
        if (isObject(value)) {
            return `${result}${getName(value)}`
        } 
        return result
    }, "")

toPureString(data)
// hello Bob and Fred How are you guys today?

Answer 1

我只想做这样的事情：

const {compose, join, map, unless, is, prop} = R
const data = ['hello', {name: 'Bob'}, 'and', {name: 'Fred'}, 'How are you guys today?']

const transform = compose(join(' '), map(unless(is(String), prop('name'))))

console.log(transform(data))

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.js"></script>

unless是一个简化if-else，除非谓词返回true，它返回原来的值，在这种情况下，它首先应用变换函数。 （when是相似的，除了它应用于改造时，谓语是真实的。）所以这个进行两个步骤，首先都转换成统一的格式，普通的字符串，然后将它们结合起来。

这可能会读更好的给你，但它们是完全等价的：

const transform = pipe(
  map(unless(is(String), prop('name'))),
  join(' '), 
)

Answer 2

您可以使用R.cond：

const { flip, is, unapply, join, useWith, prop, T, identity } = R

const isString = flip(is(String))
const isObject = flip(is(Object))
const spacer = unapply(join(' '))
const getName = useWith(spacer, [identity, prop('name')])

const toPureString = R.reduce(R.cond([
  [isString, spacer],
  [isObject, getName],
  [T, identity]
]), '')

const data = [
    "hello",
    {name: "Bob"},
    "and",
    {name: "Fred"},
    "How are you guys today?",
]

const result = toPureString(data)

console.log(result) // hello Bob and Fred How are you guys today?

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.js"></script>

Answer 3

Ramda有ifElse功能。然而，当你有多个分支您if声明变得笨拙：

const ifStr = R.ifElse(isString, v => `{result}{v}`, () => result);
return R.ifElse(isObject, v => `{result}{getName(v)}`, ifStr);

对于这种情况，我会在普通的JavaScript三元声明做到这一点：

const toPureString = R.reduce((result, value) => {
    const str = isObject(value) ? getName(value) : (isString(value) ? value : '')
    return `${result}${str}`
}, '')