Documentation can be found e.g. at MDN. Note that .split() is not a jQuery method, but a native string method.

If you use .split() on a string, then you get an array back with the substrings:

var str = 'something -- something_else';
var substr = str.split(' -- ');
// substr[0] contains "something"
// substr[1] contains "something_else"

If this value is in some field you could also do:

tRow.append($('<td>').text(=txtEntry2]').val().split(' -- ')[0])));

There are several functions in JavaScript which can be used to split a string.

1. Split - (Split a string into an array of substrings)

var str = "This is a string";

var str = "This is a string";
    var res = str.split(" ");
    console.log(res);

It is important that split gives back an array with the string chunks.

2. Substr - (Extract parts of a string)

    var str = "This is a string";
    var res = str.substr(1, 4);
    console.log(res);

3. Substring - (Extract characters from a string)

    var str = "This is a string";
    var res = str.substring(1, 4);
    console.log(res);

Reference

W3Schools Split
W3Schools Substr
W3Schools Substring

Use the .split() method. When specifying an empty string as the separator, the split() method will return an array with one element per character.

entry = prompt("Enter your name")
entryArray = entry.split("");