If
var testint = 1;
var teststr = "val";
var val1 = 5;
var val2 = 8;
var val3 = 4;
then
window[teststr + testint.toString()]
will output 5
(the value of variable val1
).
Similarly, if
var testint = 2;
var teststr = "val";
var val1 = 5;
var val2 = 8;
var val3 = 4;
the outputed value will be 8
(value of variable val2
).