尝试从 node.js 中的 url 获取时，获取“无法读取未定义的属性‘长度’”

Question

So i was trying to create a Discord-Bot which is able to lookup definitions on urbandictionary.. but i am getting an error after trying to fetch the json from their api.

const args = Array.prototype.slice.call(commandArgs);
    if (!args.length) {
    return message.channel.send('You need to supply a search term!');
    }

    const query = querystring.stringify({ term: args.join(' ') });

    const body  = await fetch(`https://api.urbandictionary.com/v0/define${query}`).then(response => response.json());

    console.log(fetch(`https://api.urbandictionary.com/v0/define${query}`).then(response => response.json()));

    if (!body.list.length) {
        return message.channel.send(`No results found for **${args.join(' ')}**.`);
    }

    const [answer] = body.list;

    const embed = new Discord.RichEmbed()
        .setColor('#EFFF00')
        .setTitle(answer.word)
        .setURL(answer.permalink)
        .addField('Definition', trim(answer.definition, 1024))
        .addField('Example', trim(answer.example, 1024))
        .addField('Rating', `${answer.thumbs_up} thumbs up. ${answer.thumbs_down} thumbs down.`);

    message.channel.send(embed);
    }

the error looks like this:

    (node:11948) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'length' of undefined
    at Client.client.on (C:\Users\Johannes\Desktop\Vladimir\main.js:176:18)
    at processTicksAndRejections (internal/process/next_tick.js:81:5)
(node:11948) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:11948) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

the console.log() function in the middle just says: "Promise { pending }"

Answer 1

If we never encountered hard problems coding we probably aren't trying hard enough. And instead of giving up you asked for help. Being smart enough to do all that puts you in a good spot.

In your code you have an await command. For this to work async needs to be placed before the beginning of the outer function. Keep in mind that await only works with promises. Also note that you have fetch once next to body and then again in the console statement. This would cause two requests when we only need one. Hope the updated snippet below helps you out.

getUrbanDictionaryDefs = async function() {
  const args = Array.prototype.slice.call(commandArgs);
  if (!args.length) {
    return message.channel.send("You need to supply a search term!");
  }

  const query = querystring.stringify({ term: args.join(" ") });

  let body;

  try {
    body = await fetch(`https://api.urbandictionary.com/v0/define${query}`);
  } catch (err) {
    console.log(err);
    return;
  }

  body = body.json();

  console.log(body);

  if (!body.list.length) {
    return message.channel.send(`No results found for **${args.join(" ")}**.`);
  }

  const [answer] = body.list;

  const embed = new Discord.RichEmbed()
    .setColor("#EFFF00")
    .setTitle(answer.word)
    .setURL(answer.permalink)
    .addField("Definition", trim(answer.definition, 1024))
    .addField("Example", trim(answer.example, 1024))
    .addField(
      "Rating",
      `${answer.thumbs_up} thumbs up. ${answer.thumbs_down} thumbs down.`
    );

  message.channel.send(embed);
};