JavaScript cannot go out and scrape data off of pages. It can make a call to a local PHP script that then goes on its behalf and grabs the data, but JavaScript (in the browser) cannot do this.
$.post("/localScript.php", { srcToGet: 'http://example.com' }, function(data){
/* From within here, data is whatever your local script sent back to us */
});
You have options like JSONP and Cross-Origin Resource Sharing at your disposal, but both of those require setting up the other end, so you cannot just choose a domain and start firing off requests for data.
Further Reading: Same origin policy
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