Pop Ups + text and mouse inputs

Hi,

I'm writing some Blockly Blocks and would like to alert the user when they do something bad (e.g. try to move a servo beyond its limits). Can I have the code generate a pop up when this happens? Something like

window.alert()

or

window.confirm()

?

Also, how do I accept text input on the terminal side of the Chrome IDE? I know I can input JavaScript functions there, but what about text strings? If not possible, then how do I write my own function that will be recognized there, so the user can type "hello" and it executes the function

hello()

Finally, is there any way to accept a mouse input? e.g.

if(LeftMouseClick)
    turnOnLED(1);

Thanks,
Rehman