JavaScript Ajax_basics Guide
AJAX (Asynchronous JavaScript and XML) communicates with servers without page reload. XMLHttpRequest is the traditional API. The guide walks through XMLHttpRequest. `const xhr = new XMLHttpRequest()`. `xhr.open("GET", url)`. `xhr.send()`. `xhr.onload = () => { if (xhr.status === 200) { const data = JSON.parse(xhr.responseText) } }`. `xhr.onerror = errorHandler`. POST: `xhr.setRequestHeader("Content-Type","application/json"); xhr.send(JSON.stringify(data))`. Upload progress: `xhr.upload.onprogress`. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.