JSON.stringify

json2str.js

const json2str = (target) => {
  switch (typeof target) {
    case 'number':
      return isNaN(target) ? 'null' : target.toString()
    case 'boolean':
      return target.toString()
    case 'string':
      return `"${target}"`
    case 'object':
      if (target === null) {
        // null
        return 'null'
      } else if (Array.isArray(target)) {
        const arr = target
          .map(item => {
            const str = json2str(item)
            return str === undefined ? 'null' : str
          })
        return `[${arr.join(',')}]`
      } else if (target.toString() === '[object Object]') {
        const arr = Object.keys(target)
          .map(key => {
            const obj = target[key]
            const str = json2str(obj)
            return str === undefined ? str : `"${key}":${str}`
          })
          .filter(item => item !== undefined)
        return `{${arr.join(',')}}`
      }
      // map
      // set
      return '{}'
    default:
      // undefined 
      // function
      return undefined
  }
}


const test = (json) => {
  if (JSON.stringify(json) === json2str(json)) {
    console.log('test successfully')
  } else {
    console.log('test failure', JSON.stringify(json), json2str(json))
  }
}
test("hello world")
test(true)
test(false)
test(0)
test(1)
test(null)
test(undefined)
test(NaN)
test(function() {})
test([0, 1])
test({0: 'ha', '1': 'hello' })