javascript for getting a textbox value to another textbox.

Question

how to get the value of a textbox in some other textbox by javascript..

for example :

if we put 100 in textbox1 so the value that will come in textbox2 should be less o equal to the 100(i.e, value of textbox1) by clicking event of textbox2.

how to get this value please give the solution sir.