get system cpu usage in javascript

Unfortunately, it's not possible to obtain system-level CPU usage in the browser with plain JavaScript. However, you can use a third-party library or Node.js to obtain the system-level CPU usage.

One of the Node.js libraries that can be used to obtain system-level CPU usage is the process module.

To access CPU usage using the process module, you can use the process.cpuUsage() method. This method returns the CPU time used by the current process in microseconds. You can use this method to calculate CPU usage percentage as follows:

const startUsage = process.cpuUsage();
// spin the CPU for 500 milliseconds
const now = Date.now();
while (Date.now() - now < 500);
const used = process.cpuUsage(startUsage);
const usagePercent = (used.user + used.system) / (500 * 1000) * 100;
console.log(`CPU usage: ${usagePercent.toFixed(2)}%`);
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This code calculates the CPU usage percentage over a 500ms period. The startUsage variable holds the CPU usage at the start of the period, and used holds the CPU usage at the end of the period. The percentage is then calculated by dividing the amount of CPU time used by the elapsed time and multiplying by 100.

Note that the exact method of obtaining the system-level CPU usage will depend on your platform and environment.