Try executing the following in JavaScript:
parseInt(\'01\'); //equals 1
parseInt(\'02\'); //equals 2
parseInt(\'03\'); //equals 3
parseInt(\'04\'); //equals
You may also, instead of using parseFloat or parseInt, use the unary operator (+).
+"01"
// => 1
+"02"
// => 2
+"03"
// => 3
+"04"
// => 4
+"05"
// => 5
+"06"
// => 6
+"07"
// => 7
+"08"
// => 8
+"09"
// => 9
and for good measure
+"09.09"
// => 9.09
MDN Link
The unary plus operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number.