Add js line breaks to strings

When working with string values it might be necessary to add some js line breaks to the string at the end of a string, or at any point where needed in the string for that matter. In some cases these kinds of characters are added to the end of a string automatically when using something like the console log method in nodejs for example. When using console log a line break character is added to the end of the standard output each time it is called. If you do not want that to happen then there is using the write method of the stdout property of the process object. In client side javaScript there is of course the break element, but that will not work so well in all situations.

If you are not familiar with escape notation and strings in javaScript now might be the time to take a look at them for this reason as well as many others. Escape notation is a way to add any character into a string including characters that might be interpreted as a return, or a way to end a string in javaScript source code.

There is more then one text pattern for line breaks depending on the operating system you want the content to work with. However for the most part you can get away with just using one or the other, many well designed applications are familiar with the different patterns and will detect what the situation is and parse accordingly. However it still makes sense to be al least somewhat aware of what these patterns are, and which might be the best choice for a given situation.

In any case this will be a quick post on line breaks and javaScript strings in both a nodejs and client environment.

1 - Basics of Line breaks and escape notation in javaScript

The first and for most way to go about injecting line breaks into strings would be to use javaScript string escape notation. There are other ways of doing so that might be a better choice when it comes to a nodejs environment, but even then you might still want to use escape notation over the os module that will hold line break string for the host operating system.

In some situations other options need to be used such as the %0D%0A pattern with URLS, and escape sequences for situations inducing injecting line breaks into some text that is being created for a textarea element or pre element. When working with html there is creating and injecting line break elements of course. However for this section I will be sticking to topics that apply to javaScript in general. I will be getting to node and client side specific examples later in this post.

So for now in this section I will be focusing on just escape notation as a way to create line breaks for a string. This kind of notation involves using a backslash followed by one or more additional characters to help inject any kind of character into a string including line breaks. Although I will be keeping these examples fairly simple I assume that you have at least some background when it comes to javaScript when it comes to making a few first steps at least.

- The source code examples in this post are on Gihub

On Github I have my test vjs repository where I have parked the source code examples that I am writing about in this post. I also have all the source code examples for my various other posts on javaScript topics.

1.1 - Basics of escape sequences in javaScript

The basic idea of sequences in javaScript is that there are certain characters that I can not just type when forming a javaScript string. One of which would be the double quite as that is used to indicate the beginning and end of a string literal. If I try to just type the string without using escape sequence that will result in a SyntaxError when I try to run the code. So then one way to go about addressing this would be to use escape sequences by just typing a backslash and then the character that I want, such as a double quote.

// This will result in a SyntaxError
//    let a = "This is a "String" ";
 
// so in order to place quotes they much be escaped
let b = "This is a \"String\"";
console.log(b);

1.2 - Line break escape sequences ( \r and \n )

When it comes to windows style line breaks you will want to start off with a carriage return follow by a new line. For posix style js line breaks forget the carriage return ans just inject a new line.

So the carriage return and new line escape notation can be used to create an object that would contain bolt major patterns of interest like this:

var eol = {
    win: '\r\n',
    posix: '\n'
},
os = 'win',
 
str = 'So this is one line. ' + eol[os] + 'And this is a new one. ' + eol[os];
 
console.log(str);

1.3 - Unicode code point escape sequence ( \u )

The utf-16 code unit escape notation will work also.

var eol = {
    win: '\u000d\u000a',
    posix: '\u000a'
},
os = 'win',
 
str = 'So this is one line. ' + eol[os] + 'And this is a new one. ' + eol[os];
 
console.log(str);

So these kinds of solutions will work well in general, but in a nodejs environment there are some properties that are typically used. So lets look at just one more example at least when it comes to this sort of thing.

2 - The os module EOL property in nodejs

Now that I covered the basics of line breaks in general it might now be a good idea to start looking into some examples that have to do with just nodejs.

2.1 - Escape notation and os module

In node there is the End Of Line property of the os module. This property will hold a carriage return plus new line value for windows systems, and just a new line value for posix. In other words the value of the End Of line property will change depending on the underlaying operating system used.

If you want consistent values regardless of the operating system you might want to stick to escape notation.

const os = require('os');
 
console.log(os.EOL === '\r\n'); // (true if windows)
console.log(os.EOL === '\n'); // (true if posix)
 
console.log( Buffer.from('\r\n').toString('hex') ); // 0d0a
console.log( '\u000d\u000a' === '\r\n'); // true
console.log( '\u000a' === '\n'); // true
 
let str = 'line one' + os.EOL +
'line two\r\n' +
'line three\n' +
'line four\u000d\u000a' +
'line five\u000a'+
'end';
process.stdout.write(str);

2.2 - The decode URI Component method

Another options that comes to mind is the decode url component method.

const eol = {
    win: decodeURIComponent('%0D%0A'),
    posix: decodeURIComponent('%0A')
}
 
console.log(Buffer.from(eol.win).toString('hex')); // 0d0a

3 - Conclusion

Having a way to find out if there is a line bake in a string is something that will come up from time to time when working out a script. In nodejs often the result of calling a command in a Linux environment will spit out results where each line is terminated with a line break, if I want to spit that output into an array I will need to know how to do that. In a Linux system the line break will typically be a single new line char, however in windows it might be a carriage return followed by a new line.

Knowing how to find out if there is a line break is important however knowing how to go about creating a line break in a string is also something that I need to do also. If I want to create a script that will do s replace all for some text from one kind of line break to another, it will require that I I not just know how to find line breaks, but also how to go about injecting one of the options that I would want to replace them. This if often a feature in most text editors, however if I where to write my own text editor a feature such as this is one thing that I would want to have in such an application.