imsky / holder
Client-side image placeholders.
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Language:JavaScript
Type:component
Requires
README
Holder renders image placeholders in browser using SVG.
Used by thousands of open source projects (including Bootstrap v3) and many other sites.
No extra requests, small bundle size, highly customizable.
Installing
- npm:
npm install holderjs
- yarn:
yarn add holderjs
- unpkg: https://unpkg.com/holderjs
- cdnjs: https://cdnjs.com/libraries/holder
- jsDelivr: https://www.jsdelivr.com/package/npm/holderjs
- Bower:
bower install holderjs
- Rails Assets:
gem 'rails-assets-holderjs'
- Meteor:
meteor add imsky:holder
- Composer:
php composer.phar update imsky/holder
- NuGet:
Install-Package Holder.js
Usage
Include holder.js
in your HTML:
<script src="holder.js"></script>
Holder will then process all images with a specific src
attribute, like this one:
<img src="holder.js/300x200">
The above tag will render as a placeholder 300 pixels wide and 200 pixels tall.
To avoid console 404 errors, you can use data-src
instead of src
.
Programmatic usage
To programmatically insert a placeholder use the run()
API:
var myImage = document.getElementById('myImage'); Holder.run({ images: myImage });
Placeholder options
Placeholder options are set through URL properties, e.g. holder.js/300x200?x=y&a=b
. Multiple options are separated by the &
character.
theme
: The theme to use for the placeholder. Example:holder.js/300x200?theme=sky
random
: Use random theme. Example:holder.js/300x200?random=yes
bg
: Background color. Example:holder.js/300x200?bg=2a2025
fg
: Foreground (text) color. Example:holder.js/300x200?fg=ffffff
text
: Custom text. Example:holder.js/300x200?text=Hello
size
: Custom text size. Defaults topt
units. Example:holder.js/300x200?size=50
font
: Custom text font. Example:holder.js/300x200?font=Helvetica
align
: Custom text alignment (left, right). Example:holder.js/300x200?align=left
outline
: Draw outline and diagonals for placeholder. Example:holder.js/300x200?outline=yes
lineWrap
: Maximum line length to image width ratio. Example:holder.js/300x200?lineWrap=0.5
Themes
Holder includes support for themes, to help placeholders blend in with your layout.
There are 6 default themes: sky
, vine
, lava
, gray
, industrial
, and social
.
Customizing themes
Themes have 5 properties: fg
, bg
, size
, font
and fontweight
. The size
property specifies the minimum font size for the theme. The fontweight
default value is bold
. You can create a sample theme like this:
Holder.addTheme("dark", { bg: "#000", fg: "#aaa", size: 11, font: "Monaco", fontweight: "normal" });
If you have a group of placeholders where you'd like to use particular text, you can do so by adding a text
property to the theme:
Holder.addTheme("thumbnail", { bg: "#fff", text: "Thumbnail" });
Using custom themes
There are two ways to use custom themes with Holder:
- Include theme at runtime to render placeholders already using the theme name
- Include theme at any point and re-render placeholders that are using the theme name
The first approach is the easiest. After you include holder.js
, add a script
tag that adds the theme you want:
<script src="holder.js"></script> <script> Holder.addTheme("bright", { bg: "white", fg: "gray", size: 12 }); </script>
The second approach requires that you call run
after you add the theme, like this:
Holder.addTheme("bright", {bg: "white", fg: "gray", size: 12}).run();
Using custom themes and domain on specific images
You can use Holder in different areas on different images with custom themes:
<img data-src="example.com/100x100?theme=simple" id="new">
Holder.run({ domain: "example.com", themes: { "simple": { bg: "#fff", fg: "#000", size: 12 } }, images: "#new" });
Inserting an image with custom theme
You can add a placeholder programmatically by chaining Holder calls:
Holder.addTheme("new", { fg: "#ccc", bg: "#000", size: 10 }).addImage("holder.js/200x100?theme=new", "body").run();
The first argument in addImage
is the src
attribute, and the second is a CSS selector of the parent element.
Text
Holder automatically adds line breaks to text that goes outside of the image boundaries. If the text is so long it goes out of both horizontal and vertical boundaries, the text is moved to the top. If you prefer to control the line breaks, you can add \n
to the text
property:
<img data-src="holder.js/300x200?text=Add \n line breaks \n anywhere.">
If you would like to disable line wrapping, set the nowrap
option to true
:
<img data-src="holder.js/300x200?text=Add \n line breaks \n anywhere.&nowrap=true">
When using the text
option, the image dimesions are not shown. To reinsert the dimension into the text, simple use the special holder_dimensions
placeholder.
<img data-src="holder.js/90px80p?theme=sky&text=Placeholder dimensions: holder_dimensions">
Placeholders using a custom font are rendered using canvas by default, due to SVG's constraints on cross-domain resource linking. If you're using only locally available fonts, you can disable this behavior by setting noFontFallback
to true
in Holder.run
options. However, if you need to render a SVG placeholder using an externally loaded font, you have to use the object
tag instead of the img
tag and add a holderjs
class to the appropriate link
tags. Here's an example:
<head> <link href="http://.../font-awesome.css" rel="stylesheet" class="holderjs"> </head> <body> <object data-src="holder.js/300x200?font=FontAwesome"></object>
Important: When testing locally, font URLs must have a http
or https
protocol defined.
Important: Fonts served from locations other than public registries (i.e. Google Fonts, Typekit, etc.) require the correct CORS headers to be set. See How to use CDN with Webfonts for more details.
<object>
placeholders work like <img>
placeholders, with the added benefit of their DOM being able to be inspected and modified. As with <img>
placeholders, the data-src
attribute is more reliable than the data
attribute.
Fluid placeholders
Important: Percentages are specified with the p
character, not with the %
character.
Specifying a dimension in percentages creates a fluid placeholder that responds to media queries.
<img data-src="holder.js/100px75?theme=social">
By default, the fluid placeholder will show its current size in pixels. To display the original dimensions, i.e. 100%x75, set the textmode
flag to literal
like so: holder.js/100px75?textmode=literal
.
Automatically sized placeholders
If you'd like to avoid Holder enforcing an image size, use the auto
flag like so:
<img data-src="holder.js/200x200?auto=yes">
The above will render a placeholder without any embedded CSS for height or width.
To show the current size of an automatically sized placeholder, set the textmode
flag to exact
like so: holder.js/200x200?auto=yes&textmode=exact
.
Preventing updates on window resize
Both fluid placeholders and automatically sized placeholders in exact mode are updated when the window is resized. To set whether or not a particular image is updated on window resize, you can use the setResizeUpdate
method like so:
var img = $('#placeholder').get(0); Holder.setResizeUpdate(img, false);
The above will pause any render updates on the specified image (which must be a DOM object).
To enable updates again, run the following:
Holder.setResizeUpdate(img, true);
This will enable updates and immediately render the placeholder.
Background placeholders
Holder can render placeholders as background images for elements with the holderjs
class, like this:
#sample {background:url(?holder.js/200x200?theme=social) no-repeat}
<div id="sample" class="holderjs"></div>
The Holder URL in CSS should have a ?
in front. Like in image placeholders, you can specify the Holder URL in a data-background-src
attribute:
<div class="holderjs" data-background-src="?holder.js/300x200"></div>
Important: Make sure to define a height and/or width for elements with background placeholders. Fluid background placeholders are not yet supported.
Runtime settings
Holder provides several options at runtime that affect the process of image generation. These are passed in through Holder.run
calls.
domain
: The domain to use for image generation. Default value:holder.js
.dataAttr
: The HTML attribute used to define a fallback to the nativesrc
attribute. Default value:data-src
.renderer
: The renderer to use. Options available:svg
,canvas
. Default value:svg
.images
: The CSS selector used for findingimg
tags. Default value:img
.objects
: The CSS selector used for findingobject
placeholders. Default value:object
.bgnodes
: The CSS selector used for finding elements that have background palceholders. Default value:body .holderjs
.stylenodes
: The CSS selector used for finding stylesheets to import into SVG placeholders. Default value:head link.holderjs
.noFontFallback
: Do not fall back to canvas if using custom fonts.noBackgroundSize
: Do not setbackground-size
for background placeholders.
Using custom settings on load
You can prevent Holder from running its default configuration by executing Holder.run
with your custom settings right after including holder.js
. However, you'll have to execute Holder.run
again to render any placeholders that use the default configuration.
Using with lazyload.js
Holder is compatible with lazyload.js
and works with both fluid and fixed-width images. For best results, run .lazyload({skip_invisible:false})
.
Using with React
When using Holder in a React component, execute Holder.run
in componentDidMount
to enable rendering after state changes. See this issue for more details.
Using with Vue
You can use Holder in Vue 2+ projects with vue-holderjs.
Using with Angular.js
You can use Holder in Angular projects with ng-holder or with angular-2-holderjs for Angular 2 projects.
Using with Meteor
Because Meteor includes scripts at the top of the document by default, the DOM may not be fully available when Holder is called. For this reason, place Holder-related code in a "DOM ready" event listener.
Using with Webpack
If you're using ProvidePlugin
in your Webpack config, make sure to configure it as follows:
plugins: [ new webpack.ProvidePlugin({ 'Holder': 'holderjs', 'holder': 'holderjs', 'window.Holder': 'holderjs' }) ]
Browser support
- Chrome
- Firefox 3+
- Safari 4+
- Internet Explorer 9+ (with partial support for 6-8)
- Opera 12+
- Android (with fallback)
Source
- GitHub: https://github.com/imsky/holder
- GitLab: https://gitlab.com/imsky/holder
License
Holder is provided under the MIT License.
Credits
Holder is a project by Ivan Malopinsky.