eval behavior in strict mode

eval.js

/* sloppy mode */
function test(arg) {
   alert(eval("var arg = 1; arg")+" "+arg); //arg in eval changes arg in func context. if you declare arg suing let it will lock in eval context.
}
test(3); //prints 1 1

/* strict mode */
function test(arg) {
   "use strict"
   alert(eval("var arg = 1; arg")+" "+arg); //arg in eval does not change arg in func context
}
test(3); //prints 1 3