如何在异步 function 中运行替换 function？

Question

I had a MongoDB and I want to change a value of a bunch of templates.

I guess I get the variable and replace the old value.

  findTemplates.forEach(async templateName => {
     const template = await getTemplate( templateName )
     const templateBody = await replaceBody( template.body )
     templateBody.replace('string', 'another-string');
  })

  async function getTemplate (siteName) {
    const id = await emailTemplate.model.findOne({
      'name.de': siteName,
      language: 'en',
      businessUnit: '24ede462ad78fd0d4fd39dfa',
    }).distinct('_id')

    const body = await emailTemplate.model.findOne({
      '_id': id,
    }).distinct('body')

    return {
      id: id,
      body: body
    }
  }

  function replaceBody( body ) {
     return body.replace('one', 'two')
  }

unfortunately, I get the following error:

UnhandledPromiseRejectionWarning: TypeError: body.replace is not a functiontemplateBodyHow can I use the replace function in my forEach async function?

Answer 1

I rewrote your sample, so I can simulate it, this sample works as you expected, but no exception was thrown. So, the only mistake I have detected was in this line:

 // You must not put await here because replace body does not return a Promise.
 const templateBody = replaceBody( template.body )

 const allTemplates = [] for (let i = 0; i <= 10; i++) { allTemplates.push({ _id: faker.random.uuid(), 'name.de': faker.internet.domainName(), language: faker.random.locale(), businessUnit: faker.random.uuid(), body: faker.lorem.paragraph() }) } const findTemplates = allTemplates.map(item => item['name.de']) const emailTemplate = { model: { findOne: params => { const found = allTemplates.find(item => params._id? item._id === params._id: item['name.de'] === params['name.de']) const result = Object.assign({}, found, params) result.distinct = function (key) { return Promise.resolve(this[key]) } return result } } } async function getTemplate (siteName) { const id = await emailTemplate.model.findOne({ 'name.de': siteName, language: 'en', businessUnit: '24ede462ad78fd0d4fd39dfa', }).distinct('_id') const body = await emailTemplate.model.findOne({ '_id': id, }).distinct('body') return { id: id, body: body } } function replaceBody( body ) { return body.replace('one', 'two') } findTemplates.forEach(async templateName => { try { const template = await getTemplate( templateName ) // You must not put await here because replace body does not return a Promise. const templateBody = replaceBody( template.body ) console.log(templateBody.replace('string', 'another-string')) } catch (err) { console.err(`Error procesing template: ${templateName}: ${err}`) } }) /** * Alternatively you can do: Promise.all(findTemplates.map(async templateName => { const template = await getTemplate( templateName ) // You must not put await here because replace body does not return a Promise. const templateBody = replaceBody( template.body ) console.log(templateBody.replace('string', 'another-string')) }).catch(err => console.err) */

 <script src="https://cdnjs.cloudflare.com/ajax/libs/Faker/3.1.0/faker.min.js"></script>

So respect to your question: How can I use the replace function in my forEach async function? The answer is you can use replace as you do (but fix the line, and check what @tj-crowder commented).

If the body is not string, then you should inspect what kind of object it is, and if it has a replace function (or not), and if this replace function returns (or not) a Promise.