Remove last four characters

var myString = "abcdefg";
var newString = myString.substr(0, myString.length-4);
// newString is now "abc"

Remove first two characters

var myString = "abcdefg";
var newString = myString_2.substr(2);
// newString is now "cdefg"

Notes

The substr function can be called on any string with two integer parameters, the second optional. If only one provided, it starts at that integer and moves to the end of the string, chopping off the start. If two parameters provided, it starts at the first number and ends at the second, chopping off the start and end as it is able.

Example

abcdefghijklmnopqrstuvwxyz

Press to Chop