Webscraping.proWorking with a Backconnect proxy service (Oxylab.io) we spent a long time looking for a way to authorize it. Originally we used JSoup to get the web pages’ content. The proxy() method can be used there when setting up the connection, yet it only accepts the host and port, no authentication is possible. One of the options that we found, was the following:
function strip_tags(str){
const tags = ['a', 'em', 'div', 'span', 'p', 'i', 'button', 'img' ];
const tagsAndContent = ['picture', 'script', 'noscript', 'source'];
for(tag of tagsAndContent){
let regex = new RegExp( '<' + tag+ '.*?</' + tag + '>', 'gim');
str = str.replace( regex ,"");
}
for(tag of tags){
let regex1 = new RegExp( '<' + tag+ '.*?>', 'gim');
let regex2 = new RegExp( '</' + tag+ '>', 'gim');
str = str.replace(regex1,"").replace(regex2,"");
}
return str;
}Often we want only a certain info from the matched content. So, groups help with that.
The following example shows how to fetch the [duplicate] entry index from the error message. For that we take 1st group, index “1”:
const regex = /Duplicate entry\s'([^']+)+'/gm;
const str = `{ Error: (conn=42434, no: 1062, SQLState: 23000) Duplicate entry '135' for key 'PRIMARY'
sql: INSERT INTO \`test\` (id , string1) values (?,?) - parameters:[[135,'string 756']]
at Object.module.exports.createError (C:\\Users\\User\\Documents\\RnD\\Node.js\\mercateo-`;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}As developers scrape data off the web, we use Node.js along with handy Cheerio scraper. When fetching .html() Cheerio parser returns the special symbols as HTML encoded entities, eg.:ä as ä ß as ß
(1) It’s not the job of a parser to preserve the original document.
(2) .html() returns an HTML representation of the parsed document, which doesn’t have to be equal to the original document.
source.