Delete a line of text in javascript

This removes the first line from a multi-line string variable - tested in Chrome version 23 on a variable which was read from file (HTML5) with line endings/breaks that showed as CRLF (carriage return + line feed) in Notepad++:

var lines = `first
second
third`;

// cut the first line:
console.log( lines.substring(lines.indexOf("\n") + 1) );

// cut the last line:
console.log( lines.substring(lines.lastIndexOf("\n") + 1, -1 ) )

The cleanest way of doing this is to use the split and join functions, which will let you manipulate the text block as an array of lines, like so:

// break the textblock into an array of lines
var lines = textblock.split('\n');
// remove one line, starting at the first position
lines.splice(0,1);
// join the array back into a single string
var newtext = lines.join('\n');