posthtml-expressions
v1.11.4TypeScript
Expressions Plugin for PostHTML
42.5K/weekUpdated 1 years agoMITUnpacked: 42.2 KB
Published by Jeff Escalante
npm install posthtml-expressions[![npm][npm]][npm-url]
[![node][node]][node-url]
[![tests][tests]][tests-url]
[![coverage][cover]][cover-url]
[![code style][style]][style-url]
Expressions Plugin
Install
``bash`
npm i -D posthtml-expressions
Usage
`js
const { readFileSync } = require('fs')
const posthtml = require('posthtml')
const expressions = require('posthtml-expressions')
posthtml(expressions({ locals: { foo: 'bar' } }))
.process(readFileSync('index.html', 'utf8'))
.then((result) => console.log(result.html))
`
This plugin provides a syntax for including local variables and expressions in your templates, and also extends custom tags to act as helpers for conditionals and looping.
You have full control over the delimiters used for injecting locals, as well as the tag names for the conditional and loop helpers, if you need them. All options that can be passed to the expressions plugin are shown below:
Options
|Option|Default|Description|
|:----:|:-----:|:----------|
| delimiters | ['{{', '}}'] | Array containing beginning and ending delimiters for escaped locals os expressions |['{{{', '}}}']
| unescapeDelimiters | | Array containing beginning and ending delimiters for unescaped locals |{}
| locals | | Object containing any local variables you want to be available inside your expressions |locals
| localsAttr | | Attribute name for the tag script which contains locals|false
| removeScriptLocals | | Will remove tag script which contains locals|['if', 'elseif', 'else']
| conditionalTags | | Array containing names for tags used for if/else statements |['switch', 'case', 'default']
| switchTags | | Array containing names for tags used for switch/case/default statements |['each']
| loopTags | | Array containing names for for loops |['scope']
| scopeTags | | Array containing names for scopes |'raw'
| ignoredTag | | String containing name of tag inside which parsing is disabled |true
| strictMode | | Boolean value set to false will not throw an exception if a value in locals not found or expression could not be evaluated|undefined
| missingLocal | | string defining the replacement value in case value not found in locals. May contain {expression} placeholder|
$3
You can inject locals into any piece of content in your html templates, other than overwriting tag names. For example, if you passed the following config to the expressions plugin:
`js`
locals: { className: 'intro', name: 'Marlo', 'status': 'checked' }
`html`
My name is {{ name }}
`html`
My name is Marlo
You can also use the script tag with the attribute locals or you custome attribute containing data to interpolate in the template.
`html
My name: {{name}}
`
html
My name: Scrum
`In addition, the use of script tag allow you to use
defined globally to assign data to variables.`js
posthtml(expressions({ locals: { foo: 'bar' } }))
.process(readFileSync('index.html', 'utf8'))
.then((result) => console.log(result.html))
`html
My name: {{name}}
Foo: {{foo}}
`html
My name: {{name}}
Foo: bar
`
#### Missing locals
What to produce in case of referencing a value not in can be configured by the missingLocal and strictMode options.When
strictMode is true (default) and leaving the missingLocal option undefined, then "'foo' is not defined" exception is thrown.Setting
strictMode false and leaving the missingLocal option undefined results the string undefined in the outputSetting the option
missingLocal to a string will produce that string in the output regardless the value of option strictMode. missingLocal can contain the placeholder {local} which will be replaced with the name of the missing local in the output. This solution allows to:
1. Silently ignore missing locals by setting missingLocal to ""
2. Include the name of the missing local in the output to help detect the which value is missing in like "#Missing value: {local}"|
missingLocal|strictMode|output|
|:----:|:-----:|:----------|
| undefined (default) | true (default) | Error is thrown |
| undefined (default) | false | 'undefined' |
| '' | false/true | '' (not output)
| {local} | false/true | original reference like {{foo}}$3
By default, special characters will be escaped so that they show up as text, rather than html code. For example, if you had a local containing valid html as such:
js
locals: { statement: 'wow!' }
`html
The fox said, {{ statement }}
`html
The fox said, <strong>wow!<strong>
`In your browser, you would see the angle brackets, and it would appear as intended. However, if you wanted it instead to be parsed as html, you would need to use the
, which by default are three curly brackets, like this:`html
The fox said, {{{ strongStatement }}}
`In this case, your code would render as html:
html
The fox said, wow!
`$3
You are not limited to just directly rendering local variables either, you can include any type of javascript expressions and it will be evaluated, with the result rendered. For example:
html
in production!
`With this in mind, it is strongly recommended to limit the number and complexity of expressions that are run directly in your template. You can always move the logic back to your config file and provide a function to the locals object for a smoother and easier result. For example:
js
locals: {
isProduction: (env) => env === 'production' ? 'active' : 'hidden'
}
`html
in production!
`#### Ignoring Expressions
Many JavaScript frameworks use
and }} as expression delimiters. It can even happen that another framework uses the same _custom_ delimiters you have defined in this plugin.You can tell the plugin to completely ignore an expression by prepending
@ to the delimiters:`html
The @{{ foo }} is strong with this one.
`Result:
html
The {{ foo }} is strong with this one.
`$3
Conditional logic uses normal html tags, and modifies/replaces them with the results of the logic. If there is any chance of a conflict with other custom tag names, you are welcome to change the tag names this plugin looks for in the options. For example, given the following config:
js
locals: { foo: 'foo' }
`html
Foo really is bar! Revolutionary!
Foo is wow, oh man.
Foo is probably just foo in the end.
`html
Foo is probably just foo in the end.
`Anything in the
attribute is evaluated directly as an expressions.It should be noted that this is slightly cleaner-looking if you are using the SugarML parser. But then again so is every other part of html.
`sml
if(condition="foo === 'bar'")
p Foo really is bar! Revolutionary!elseif(condition="foo === 'wow'")
p Foo is wow, oh man.
else
p Foo is probably just foo in the end.
`####
Type:
\
Default: ['if', 'elseif', 'else']You can define custom tag names to use for creating a conditional.
Example:
js
conditionalTags: ['when', 'elsewhen', 'otherwise']
`html
Foo really is bar! Revolutionary!
Foo is wow, oh man.
Foo is probably just foo in the end.
`Note: tag names must be in the exact order as the default ones.
$3
Switch statements act like streamline conditionals. They are useful for when you want to compare a single variable against a series of constants.
js
locals: { foo: 'foo' }
`html
Foo really is bar! Revolutionary!
Foo is wow, oh man.
Foo is probably just foo in the end.
`html
Foo is probably just foo in the end.
`Anything in the
attribute is evaluated directly as an expressions.####
switchTagsType:
\
Default: ['switch', 'case', 'default']You can define custom tag names to use when creating a switch.
Example:
js
switchTags: ['clause', 'when', 'fallback']
`html
Foo really is bar! Revolutionary!
Foo is wow, oh man.
Foo is probably just foo in the end.
`Note: tag names must be in the exact order as the default ones.
$3
You can use the
tag to build loops. It works with both arrays and objects. For example:`js
locals: {
array: ['foo', 'bar'],
object: { foo: 'bar' }
}
`Array
html
{{ index }}: {{ item }}
`html
1: foo
2: bar
`Object
html
{{ key }}: {{ value }}
`html
foo: bar
`The value of the
attribute is not a pure expressions evaluation, and it does have a tiny and simple custom parser. Essentially, it starts with one or more variable declarations, comma-separated, followed by the word in, followed by an expressions.
`html
{{ item }}
`So you don't need to declare all the available variables (in this case, the index is skipped), and the expressions after
doesn't need to be a local variable, it can be any expressions.####
loopTagsType:
\
Default: ['each']You can define custom tag names to use for creating loops:
Example:
js
loopTags: ['each', 'for']
`You can now also use the
tag when writing a loop:`html
{{ item }}
`#### Loop meta
Inside a loop, you have access to a special
object, which contains information about the loop currently being executed:-
loop.index - the current iteration of the loop (0 indexed)
- loop.remaining - number of iterations until the end (0 indexed)
- loop.first - boolean indicating if it's the first iteration
- loop.last - boolean indicating if it's the last iteration
- loop.length - total number of itemsExample:
`html
Item value: {{ item }}
Current iteration of the loop: {{ loop.index }}
Number of iterations until the end: {{ loop.remaining }}
This {{ loop.first ? 'is' : 'is not' }} the first iteration
This {{ loop.last ? 'is' : 'is not' }} the last iteration
Total number of items: {{ loop.length }}
`$3
You can replace locals inside certain area wrapped in a
tag. For example you can use it after posthtml-include`js
locals: {
author: { name: 'John'},
editor: { name: 'Jeff'}
}
`html
`html
`####
Type:
\
Default: ['scope']You can define a custom tag name to use for creating scopes:
Example:
js
scopeTags: ['context']
`You can now also use the
tag when writing a scope:`html
`$3
Anything inside this tag will not be parsed, allowing you to output delimiters and anything the plugin would normally parse, in their original form.
html
Output {{ foo }} as-is
`html
Output {{ foo }} as-is
`You can customize the name of the tag:
js
var opts = {
ignoredTag: 'verbatim',
locals: { foo: 'bar' } }
}posthtml(expressions(opts))
.process(readFileSync('index.html', 'utf8'))
.then((result) => console.log(result.html))
`html
Output {{ foo }} as-is
`html
Output {{ foo }} as-is
``Maintainers
Jeff Escalante | Denis Malinochkin |
Contributors
Michael Ciniawsky | Krillin | Cosmin Popovici |
[npm]: https://img.shields.io/npm/v/posthtml-expressions.svg
[npm-url]: https://npmjs.com/package/posthtml-expressions
[node]: https://img.shields.io/node/v/posthtml-expressions.svg
[node-url]: https://nodejs.org/
[deps]: https://david-dm.org/posthtml/posthtml-expressions.svg
[deps-url]: https://david-dm.org/posthtml/posthtml-expressions
[tests]: https://github.com/posthtml/posthtml-expressions/workflows/Actions%20Status/badge.svg?style=flat-square
[tests-url]: https://github.com/posthtml/posthtml-expressions/actions?query=workflow%3A%22CI+tests%22
[cover]: https://coveralls.io/repos/github/posthtml/posthtml-expressions/badge.svg
[cover-url]: https://coveralls.io/github/posthtml/posthtml-expressions
[style]: https://img.shields.io/badge/code%20style-standard-yellow.svg
[style-url]: http://standardjs.com/