使用正则表达式拆分在数组中创建2个空元素

Question

I need to split a string into 2 pieces using regex, so I used the following code:

var str = "This is a test";
var list = str.split(/(test)/);

Required output:

list = ["This is a ", "test"]

Instead of 2 this gives me 3 elements in the array (last one is empty). I understand that regex finds nothing after the 2nd match so it adds an empty (3rd) element. Is there any way that I can modify my code so I get exactly 2 elements thus avoiding the last empty element?

Note: the above code is a simplified version for which we can use other options besides regex but I would have to use regex.

Answer 1

var str = "This is a test";

var list = str.split(/(test)/,2);

list: ["This is a ", "test"]

Answer 2

Perhaps overkill if you can guarantee that you are only expecting an array of length two but given the nature of the question a more robust solution may be to use Array.filter to remove all empty strings from the array - including entries in the middle of the array which would arise from several delimiters appearing next to each other in your input string.

var list = str.split(/(test)/).filter(
    function(v){ return v!=null && v!='' }
);

Answer 3

You can try with checking if last element is empty or not:

var last = list.pop();
    last.length || list.push(last);

or:

list[list.length-1].length || list.pop();

or even shorter:

list.slice(-1)[0].length || list.pop();

To handle first empty element ( test was there as @Kobi suggested) use:

list[0].length || list.shift();

Answer 4

This is giving me the results you want:

var str = "This is a test";
var list = str.split(/(?=test)/g);

(?= is a lookahead, it doesn't capture the word test so that stays in the array after splitting.