🧭 Timeout Behavior

• Browsers enforce ≥4ms delay if a callback is scheduled ≥5 times.
• Inactivity, streaming, or loading states can slow timers.
• Timers continue during modal dialogs (alert, confirm, prompt).

window.requestIdleCallback(cb); // Runs during browser's idle time

📁 File & Blob APIs

input.files || e.dataTransfer.files; // => Blob[]
const reader = new FileReader();
reader.readAsDataURL(file) //reader has many events
img.src = URL.createObjectURL(file);  //image preview

🗺️ Location & Navigator API

window.location

href, pathname, search, hash

location.assign(url);
location.replace(url);
location.reload(true);
new URLSearchParams(location.search); // Like a Map

navigator

Access user agent and device info:

navigator.userAgentData.brands
navigator.deviceMemory
navigator.language

Beacon API (send lightweight analytics):

navigator.sendBeacon(url, data);

🕹️ History API