ejs/README.md

# EJS

Embedded JavaScript templates

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## Installation

```bash
$ npm install ejs
```

## Features

  * Control flow with `<% %>`
  * Escaped output with `<%= %>` (escape function configurable)
  * Unescaped raw output with `<%- %>`
  * Newline-trim mode ('newline slurping') with `-%>` ending tag
  * Whitespace-trim mode (slurp all whitespace) for control flow with `<%_ _%>`
  * Custom delimiters (e.g., use `<? ?>` instead of `<% %>`)
  * Includes
  * Client-side support
  * Static caching of intermediate JavaScript
  * Static caching of templates
  * Complies with the [Express](http://expressjs.com) view system

## Example

```ejs
<% if (user) { %>
  <h2><%= user.name %></h2>
<% } %>
```

Try EJS online at: https://ionicabizau.github.io/ejs-playground/.

## Usage

```javascript
let template = ejs.compile(str, options);
template(data);
// => Rendered HTML string

ejs.render(str, data, options);
// => Rendered HTML string

ejs.renderFile(filename, data, options, function(err, str){
    // str => Rendered HTML string
});
```

It is also possible to use `ejs.render(dataAndOptions);` where you pass
everything in a single object. In that case, you'll end up with local variables
for all the passed options. However, be aware that your code could break if we
add an option with the same name as one of your data object's properties.
Therefore, we do not recommend using this shortcut.

## Options

  - `cache`                 Compiled functions are cached, requires `filename`
  - `filename`              The name of the file being rendered. Not required if you
    are using `renderFile()`. Used by `cache` to key caches, and for includes.
  - `root`                  Set project root for includes with an absolute path (/file.ejs).
  - `context`               Function execution context
  - `compileDebug`          When `false` no debug instrumentation is compiled
  - `client`                When `true`, compiles a function that can be rendered
    in the browser without needing to load the EJS Runtime
    ([ejs.min.js](https://github.com/mde/ejs/releases/latest)).
  - `delimiter`             Character to use with angle brackets for open/close
  - `debug`                 Output generated function body
  - `strict`                When set to `true`, generated function is in strict mode
  - `_with`                 Whether or not to use `with() {}` constructs. If `false`
    then the locals will be stored in the `locals` object. Set to `false` in strict mode.
  - `destructuredLocals`    An array of local variables that are always destructured from
    the locals object, available even in strict mode.
  - `localsName`            Name to use for the object storing local variables when not using
    `with` Defaults to `locals`
  - `rmWhitespace`          Remove all safe-to-remove whitespace, including leading
    and trailing whitespace. It also enables a safer version of `-%>` line
    slurping for all scriptlet tags (it does not strip new lines of tags in
    the middle of a line).
  - `escape`                The escaping function used with `<%=` construct. It is
    used in rendering and is `.toString()`ed in the generation of client functions.
    (By default escapes XML).
  - `outputFunctionName`    Set to a string (e.g., 'echo' or 'print') for a function to print
    output inside scriptlet tags.
  - `async`                 When `true`, EJS will use an async function for rendering. (Depends
    on async/await support in the JS runtime.

This project uses [JSDoc](http://usejsdoc.org/). For the full public API
documentation, clone the repository and run `npm run doc`. This will run JSDoc
with the proper options and output the documentation to `out/`. If you want
the both the public & private API docs, run `npm run devdoc` instead.

## Tags

  - `<%`              'Scriptlet' tag, for control-flow, no output
  - `<%_`             'Whitespace Slurping' Scriptlet tag, strips all whitespace before it
  - `<%=`             Outputs the value into the template (escaped)
  - `<%-`             Outputs the unescaped value into the template
  - `<%#`             Comment tag, no execution, no output
  - `<%%`             Outputs a literal '<%'
  - `%%>`             Outputs a literal '%>'
  - `%>`              Plain ending tag
  - `-%>`             Trim-mode ('newline slurp') tag, trims following newline
  - `_%>`             'Whitespace Slurping' ending tag, removes all whitespace after it

For the full syntax documentation, please see [docs/syntax.md](https://github.com/mde/ejs/blob/master/docs/syntax.md).

## Includes

Includes either have to be an absolute path, or, if not, are assumed as
relative to the template with the `include` call. For example if you are
including `./views/user/show.ejs` from `./views/users.ejs` you would
use `<%- include('user/show') %>`.

You must specify the `filename` option for the template with the `include`
call unless you are using `renderFile()`.

You'll likely want to use the raw output tag (`<%-`) with your include to avoid
double-escaping the HTML output.

```ejs
<ul>
  <% users.forEach(function(user){ %>
    <%- include('user/show', {user: user}) %>
  <% }); %>
</ul>
```

Includes are inserted at runtime, so you can use variables for the path in the
`include` call (for example `<%- include(somePath) %>`). Variables in your
top-level data object are available to all your includes, but local variables
need to be passed down.

NOTE: Include preprocessor directives (`<% include user/show %>`) are
still supported.

## Custom delimiters

Custom delimiters can be applied on a per-template basis, or globally:

```javascript
let ejs = require('ejs'),
    users = ['geddy', 'neil', 'alex'];

// Just one template
ejs.render('<?= users.join(" | "); ?>', {users: users}, {delimiter: '?'});
// => 'geddy | neil | alex'

// Or globally
ejs.delimiter = '$';
ejs.render('<$= users.join(" | "); $>', {users: users});
// => 'geddy | neil | alex'
```

## Caching

EJS ships with a basic in-process cache for caching the intermediate JavaScript
functions used to render templates. It's easy to plug in LRU caching using
Node's `lru-cache` library:

```javascript
let ejs = require('ejs'),
    LRU = require('lru-cache');
ejs.cache = LRU(100); // LRU cache with 100-item limit
```

If you want to clear the EJS cache, call `ejs.clearCache`. If you're using the
LRU cache and need a different limit, simple reset `ejs.cache` to a new instance
of the LRU.

## Custom file loader

The default file loader is `fs.readFileSync`, if you want to customize it, you can set ejs.fileLoader.

```javascript
let ejs = require('ejs');
let myFileLoad = function (filePath) {
  return 'myFileLoad: ' + fs.readFileSync(filePath);
};

ejs.fileLoader = myFileLoad;
```

With this feature, you can preprocess the template before reading it.

## Layouts

EJS does not specifically support blocks, but layouts can be implemented by
including headers and footers, like so:


```ejs
<%- include('header') -%>
<h1>
  Title
</h1>
<p>
  My page
</p>
<%- include('footer') -%>
```

## Client-side support

Go to the [Latest Release](https://github.com/mde/ejs/releases/latest), download
`./ejs.js` or `./ejs.min.js`. Alternately, you can compile it yourself by cloning
the repository and running `jake build` (or `$(npm bin)/jake build` if jake is
not installed globally).

Include one of these files on your page, and `ejs` should be available globally.

### Example

```html
<div id="output"></div>
<script src="ejs.min.js"></script>
<script>
  let people = ['geddy', 'neil', 'alex'],
      html = ejs.render('<%= people.join(", "); %>', {people: people});
  // With jQuery:
  $('#output').html(html);
  // Vanilla JS:
  document.getElementById('output').innerHTML = html;
</script>
```

### Caveats

Most of EJS will work as expected; however, there are a few things to note:

1. Obviously, since you do not have access to the filesystem, `ejs.renderFile()` won't work.
2. For the same reason, `include`s do not work unless you use an `include callback`. Here is an example:
  ```javascript
  let str = "Hello <%= include('file', {person: 'John'}); %>",
      fn = ejs.compile(str, {client: true});

  fn(data, null, function(path, d){ // include callback
    // path -> 'file'
    // d -> {person: 'John'}
    // Put your code here
    // Return the contents of file as a string
  }); // returns rendered string
  ```

See the [examples folder](https://github.com/mde/ejs/tree/master/examples) for more details.

### IDE Integration with Syntax Highlighting

VSCode:Javascript EJS by *DigitalBrainstem*

## Related projects

There are a number of implementations of EJS:

 * TJ's implementation, the v1 of this library: https://github.com/tj/ejs
 * Jupiter Consulting's EJS: http://www.embeddedjs.com/
 * EJS Embedded JavaScript Framework on Google Code: https://code.google.com/p/embeddedjavascript/
 * Sam Stephenson's Ruby implementation: https://rubygems.org/gems/ejs
 * Erubis, an ERB implementation which also runs JavaScript: http://www.kuwata-lab.com/erubis/users-guide.04.html#lang-javascript
 * DigitalBrainstem EJS Language support: https://github.com/Digitalbrainstem/ejs-grammar

## License

Licensed under the Apache License, Version 2.0
(<http://www.apache.org/licenses/LICENSE-2.0>)

- - -
EJS Embedded JavaScript templates copyright 2112
mde@fleegix.org.