7 ways to create multi-line strings in javascript_javascript skills

There is no standard representation method of multi-line strings in JS, but when using templates, in order to ensure the readability of the template, we inevitably use multi-line strings, so various methods have emerged. , here is a jade template as an example to briefly summarize and compare.

1. Addition of strings

This is the easiest and most commonly used form, as follows

Copy code The code is as follows:

var tmpl =''
'!!! 5'
'html'
' include header'
' body'
' //if IE 6'
' ' .alert.alert-error'
' center Sorry, we do not support IE6, please upgrade your browser'
' ' a(href="http://windows.microsoft.com/zh-CN/internet-explorer/download-ie") | IE8 official download'
' a(href="https://www .google.com/intl/en/chrome/browser/") | Chrome download'
' include head'
' .container'
' .row-fluid'
' .span8'
' block main'
' include pagerbar'
' .span4'
' include sidebar' ' include footer'
' include script'

Advantages:

Easy to understand, simple, and reliable

Flexible enough to add js logic in a single string

Disadvantages:

is not a multi-line string in the true sense. If you want real multi-line, you need to add n

. A lot of numbers look like stars, a lot of ' and ", ugly

2. Use backslash

This is called line continuation character. This is not a very common way, but once used, it is still very addictive. Just add One character

Copy code The code is as follows:

var tmpl ='
!!! 5
html
include header
body
//if IE 6
.alert.alert-error
center Sorry, we do not support IE6, please upgrade your browser
A (href = "http://windows.microsoft.com/zh-in/internet-emplorer/download-d-d-di") | IE8 official download
a (href = "https://www.google.com /intl/en/chrome/browser/") | Chrome download
include head
.container
.row-fluid
.span8
block main
include pagerbar
. span4
include sidebar
include footer
include script'


Advantages:

Simple, each line only needs one more
Efficient! This method is the fastest on most browsers,

Disadvantages:

Fatal flaw, each line must not have spaces, otherwise a direct script error
is not a true multi-line string. If you want real multi-line strings, you need to add n
yourself. Most js engines support it, but it is not part of ECMAScript

3. String array join

Copy code The code is as follows:

var tmpl = [
'!!! 5 ' ,
'html' ,
' include header' ,
' body' ,
' //if IE 6' ,
' .alert.alert-error' ,
' center Sorry, we do not support IE6, please upgrade your browser' ,
' ' center a(href="http://windows.microsoft.com/zh-CN/internet-explorer/download-ie") | IE8 official download' ,
' include head' ,
' .container' ,
' .row-fluid' ,
' .span8' ,
' block main' ,
' include pagerbar' ,
' .span4' ,
' include sidebar' ,
' include footer' ,
' include script'].join('n');

Advantages:
Real multi-line string

Easy to understand, simple and reliable
Flexible enough to add js logic in a single string

Disadvantages:

A lot of numbers and ', ", ugly

5. String.prototype.concat

Copy code The code is as follows:

var tmpl = String.prototype.concat.call(
'!!! 5' ,
'html' ,
' include header' ,
' body' ,
' //if IE 6' ,
' .alert.alert-error' ,
center Sorry, we do not support IE6, please upgrade your browser' ,
' a(href ="http://windows.microsoft.com/zh-CN/internet-explorer/download-ie") | IE8 official download' ,
' ' a(href="https://www.google.com/ intl/en/chrome/browser/") | Chrome download' ,
' include head' ,
' .container' ,
' .row-fluid' ,
' .span8' ,
' block main' ,
' include pagerbar' ,
' .span4' ,
' include sidebar' ,
' include footer' ,
' include script');


Advantages:

Not commonly used, in fact the concat method of strings is far less common
Easy to understand, simple and reliable
Flexible enough to add js logic to a single string

Disadvantages:

Not really a multi-line string
A lot of ',',", ugly

5. heredoc

This is a very clever solution, using the toString method of function

Copy the code The code is as follows:

function heredoc(fn) {
return fn.toString().split('n').slice(1,-1).join('n') 'n'
}

var tmpl = heredoc(function(){/*
!!! 5
html
include header
body
//if IE 6
.alert.alert- error
                                                                                                                                                                                                                      IE8 official download
a(href="https://www.google.com/intl/en/chrome/browser/") | Chrome download
include head
.container
.row- fluid
.span8
include sidebar
include footer
include script
*/});


Advantages:

No need to write any extra characters in the template string, clean and simpleA true multi-line string, with Oh

Disadvantages:

You cannot add js logic in a single string

It is easy to be compressed by the compressor. Yui compressor can use /*! to avoid being compressed. uglifyjs and gcc can also be configured through options not to delete specific comments. This is not a big problem

6. coffeescript

It is equivalent to changing a language. In fact, it is a great choice to implement the functions that are missing in this language through a language like coffeescript that uses js as the compilation target.

Copy code

The code is as follows:

var tmpl = """
!!! 5
html
include header
body
//if IE 6
.alert.alert-error I'm sorry, we don't support IE6, please upgrade your browser
a (href = "http://windows.microsoft.com/zh-cn/internet-download-down Download
a(href="https://www.google.com/intl/en/chrome/browser/") | Chrome Download
include head
.container
.row-fluid
.span8
Include sidebar
include footer
include script
"""

Advantages:

Easy to understand, simple and reliable

Disadvantages:

Need to know coffeescript

The entire file needs to be written in coffeescript

7. ES6

ES6 has a new feature, Template Strings. This is the first time that multi-line strings are implemented at the language level. Open Enable in chrome canary Experimental JavaScript can use this feature, and typescript will also support this method


Copy code

The code is as follows:var tmpl = `!!! 5

html

include header
body
//if IE 6
.alert.alert-error
Center Sorry , we do not support IE6, please upgrade your browser
a(href="http://windows.microsoft.com/zh-CN/internet-explorer/download-ie") | IE8 official download
a(href="https://www.google.com/intl/en/chrome/browser/") | Chrome download
include head
.container
.row-fluid
.span8
block main
include pagerbar
.span4
include sidebar
include footer
include script`

Advantages:

Easy to understand, native support

True multi-line strings
Disadvantages:

Limited JS engine support

8. Summary

After seeing these writing methods, how do you choose? If you are using coffeescript, feel free to use the multi-line string writing method it supports; if you are on the client and you have solved the problem of removing comments in your compressor, it is recommended to use heredoc; if you cannot solve the problem of the compressor Question, use backslashes to connect. You only need to add one character to each line.