2025-06-11 22:23:49 +08:00

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# Eta
[Eta](https://eta.js.org/) is an embedded JS template engine for Node, Deno, and the browser. Lighweight, fast, and pluggable. Written in TypeScript.
## Usage
There are 2 modes for rendering:
### Pre-rendered (Default)
The values of the expressions are evaluated and added to the template during compilation of the [result page](../features/result.html.md).
The values of all expressions should be supplied in advance using [custom settings](../advanced/custom-settings.html.md) to the property `template.data` which accepts an object of key-value pairs.
Example: This provides the value of the expression `name`
```json title="Custom Settings"
{
"template": {
"data": {
"name": "LiveCodes"
}
}
}
```
[Full example below](#pre-rendered)
### Dynamic
To use this mode, the property `template.prerender` in [custom settings](../advanced/custom-settings.html.md) should be set to `false`.
Example:
```json title="Custom Settings"
{
"template": {
"prerender": false
}
}
```
In this mode, in addition to values supplied in custom settings (see above), expressions can have values that are evaluated during the [result page](../features/result.html.md) runtime.
This can be achieved in JavaScript (or any [language](../languages/index.html.md) that compiles to it) by assigning `window.livecodes.templateData` to an object with the data.
Please note that template rendering occurs on [page load](https://developer.mozilla.org/en-US/docs/Web/API/Window/load_event), so the assignment must occur before that.
Example:
```js title="Script Editor (JS)"
window.livecodes.templateData = { name: 'LiveCodes' };
```
[Full example below](#dynamic-1)
## Language Info
### Name
`eta`
### Extension
`.eta`
### Editor
`markup`
## Compiler
The official [Eta compiler](https://www.npmjs.com/package/eta).
### Version
`eta`: v3.4.0
## Code Formatting
Using [Prettier](https://prettier.io/).
## Custom Settings
[Custom settings](../advanced/custom-settings.html.md) added to the property `eta` are passed as a JSON object to the [`Eta.render`](https://eta.js.org/docs/api/rendering) method during compile. Please check the [documentation](https://eta.js.org/docs/api/configuration) for full reference.
Please note that custom settings should be valid JSON (i.e. functions are not allowed).
**Example:**
```json title="Custom Settings"
{
"eta": {
"varName": "data"
}
}
```
## Example Usage
import LiveCodes from '../../src/components/LiveCodes.tsx';
### Pre-rendered
export const config = {markup: {language: 'eta', content: 'Hello <%= it.name %>!'}, customSettings: {"template": {"data": {"name": "LiveCodes"}}}};
export const params = {compiled: 'open'};
<LiveCodes config={config} params={params}></LiveCodes>
### Dynamic
export const config2 = {markup: {language: 'eta', content: 'Hello <%= it.name %>!'}, script: {language: 'javascript', content: 'window.livecodes.templateData = { name: "LiveCodes" };'}, customSettings: {"template": {"prerender": false}}, activeEditor: 'script'};
<LiveCodes config={config2}></LiveCodes>
## Links
- [Official website](https://eta.js.org/)
- [Documentation](https://eta.js.org/docs/learn)