He was writing a small page the involved doing a bunch of calculations based on some options. Various numeric values to be used in those calculations were stored in a set of arrays, sort of like this:
var foo = new Array(4001, 1234, 5678);var bar = new Array(5921);
While foo was behaving nicely
[4001, 1234, 5678]
bar kept showing up like this:
[undefined, undefined, undefined, undefined, 5917 more...]
Have you figured out the problem yet?
var a = new Array(1,2,3,4); //This contains the values 1,2,3,4var a = new Array();a = 1;a = 2; //This array now has the values 1,2var a = [1,2,3,4]; //Literal notation, this is the ideal way to declare an array.var a = new Array(5); //This is an empty array with 5 elements
See that last one? Our code for bar up above doesn't realize we want to put the value 5921 into element 0 of the array. It thinks we wanted to create an empty array with 5921 elements!
Changing the code to this fixed the problem:
var bar = new Array(5921,0);