Tell me my screen resolution! Output the device's screen resolution in the specific format of [width]x[height](without the brackets). For example, an output could be 1440x900.

Here's an online tester that you can use to check your own screen resolution.
JavaScript (ES6), 32 bytes
(_=screen)=&gt;_.width+&quot;x&quot;+_.height

Outputs as function return. Add f= at the beginning and invoke like f(). Uses parameter-initializing to initialize the parameter _ to screen object. The rest is self-explanatory.


f=(_=screen)=&gt;_.width+"x"+_.height
console.log(f())



Note: Passing an argument to this function will cause it to fail.

JavaScript (Previous Solution), 35 bytes


with(screen)alert(width+"x"+height)



Never thought I will one day use with! I don't think this can be golfed further.