This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
cpuSleepAllowed property determines if the device's CPU will sleep after the screen is disabled. Setting this attribute to false will prevent the device from entering the suspend state.
var isTheCPUAllowedToSleep = navigator.mozPower.cpuSleepAllowed
Return a boolean.
Not part of any specification.