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ViewsHow to use async/await inside promise executor to read pdf content?
import axios from 'axios'
export const findNumberOfPages = async pdfUrl => {
return new Promise(async (resolve, reject) => {
try {
const response = await axios.get(pdfUrl, {
headers: { 'Content-Type': 'application/pdf' }
})
const reader = new FileReader()
reader.readAsBinaryString(new Blob([response.data]))
reader.onloadend = () => {
const pages = reader.result.match(/\/Type[\s]*\/Page[^s]/g)
const count = pages?.length
resolve(count)
}
} catch (error) {
reject(new Error(`Error when fetching pdf: ${error.message}`))
}
})
}
I'm adding a utility to get number of pages in a pdf(https url) using File Reader API.
But eslint shows an error, Promise executor functions should not be async. (no-async-promise-executor)standard(no-async-promise-executor), and I want to await the axios request to get the pdf response. How can i await the axios request and resolve the number of pages on onloadend of FileReader?
1 answers
Answer question0
You don't need the promise constructor here. You would (although not quite in that way) if you had to use FileReader, but you don't, Blob has a text method that reads the blob as text:
import axios from 'axios';
export const findNumberOfPages = async pdfUrl => {
try {
const response = await axios.get(pdfUrl, {
headers: { 'Content-Type': 'application/pdf' }
});
const result = await new Blob([response.data]).text();
const pages = result.match(/\/Type[\s]*\/Page[^s]/g);
const count = pages?.length;
return count;
} catch (error) {
throw new Error(`Error when fetching pdf: ${error.message}`);
}
};
I don't use axios, but I suspect that axios.get call is a bit off. You've specified a Content-Type, but you're not sending data (the Content-Type request header specifies the type of data you're sending, not receiving). Also, I suspect you don't need the Blob part of this at all.
Using the built-in fetch instead, I'd expect you could do it like this:
import axios from 'axios';
export const findNumberOfPages = async pdfUrl => {
try {
const response = await fetch(pdfUrl);
if (!response.ok) {
throw new Error(`HTTP error ${response.status}`);
}
const result = await response.text();
const pages = result.match(/\/Type[\s]*\/Page[^s]/g);
const count = pages?.length;
return count;
} catch (error) {
throw new Error(`Error when fetching pdf: ${error.message}`);
}
};