# Echo [](https://travis-ci.org/toddmotto/echo)
Echo is a standalone JavaScript lazy-loading image tool. Echo is fast, less than 1KB and uses HTML5 data-* attributes. Check out a [demo](http://toddmotto.com/labs/echo). Echo works in IE8+.
Using Echo.js is simple, just add the image you wish to load to a `data-echo` attribute.
```html
```
### .init() API (options)
The `init()` API takes a few options
#### offset
Type: `Integer` Default: `0`
The `offset` option allows you to specify how far below the viewport you want Echo to _begin_ loading your images. If you specify `0`, Echo will load your image as soon as it is visible in the viewport, if you want to load _1000px_ below the viewport, use `1000`.
#### throttle
Type: `Integer` Default: `250`
The throttle is managed by an internal function that prevents performance issues from continuous firing of `window.onscroll` events. Using a throttle will set a small timeout when the user scrolls and will keep throttling until the user stops. The default is `250` milliseconds.
### .render() API
Echo's callback `render()` can be used to make Echo poll your images when you're not scrolling, for instance if you've got a filter layout that swaps images but does not scroll, you need to call the internal functions without scrolling. Use `render()` for this:
```js
Echo.render();
```
Using `render()` is also throttled, which means you can bind it to a `window.onresize` event and it will be optimised for performance in the same way `window.onscroll` is.
## Installing with Bower
To install Echo into your project using Bower, use the GitHub repository hook:
```
bower install https://github.com/toddmotto/echo.git
```
## Manual installation
Drop your files into your required folders, make sure you're using the file(s) from the `dist` folder, which is the compiled production-ready code. Ensure you place the script before the closing `` tag so the DOM tree is populated when the script runs.
## Configuring Echo
Add the image that needs to load when visible in a `data-echo` attribute:
```html