str.spilt（）.length

This statement is incomplete and does not make sense on its own. It seems like it is missing some code or context.

The ".split()" method is used to split a string into an array of substrings based on a specified separator. The "length" property is used to determine the number of elements in an array.

So, if we have a string "Hello, World!" and we use the ".split()" method to split it based on the comma separator, like this:

var string = "Hello, World!";
var array = string.split(",");
console.log(array.length);

The output will be 2, because the original string was split into two substrings - "Hello" and " World!". So, the code above will log the length of the resulting array, which is 2.