Img-placeholder-src NPM

img-placeholder-src

helper for using structured data to populate various image placeholder sources. 18kb/6kb

Demo showing keys features. For code examples and docs, see below.

Install

npm install img-placeholder-src --save

Usage

Node

var IPS = require('img-placeholder-src');
var ips = new IPS;

var imageData = {
  height: 100,
  width: 100
};

var src = ips.src(imageData, 'placeholdit');
console.log(src);
/*
http://placehold.it/100x100
*/

var IPS = require('img-placeholder-src');
var ips = new IPS;

var srcsetData = [
  {
    height: 100,
    width: 100
  },
  {
    height: 200,
    width: 200
  }
];

var srcset = ips.srcset(srcsetData, 'placeholdit');
console.log(srcset);
/*
http://placehold.it/100x100 100w, http://placehold.it/200x200 200w
*/

Browser

Download the bundled script file img-placeholder-src.bundle.js. There is also a none bundle version available, but you will have to include the srcset dependency yourself.

<!DOCTYPE html>
<html lang="en">
<head>
  <script src="img-placeholder-src.bundle.js"></script>
  <script>
  // Initialize/Configure IPS
  var ips = new IPS({
    serviceOverride: 'fillmurray'
  });
  // Create image data object
  var imageData = {
    height: 100,
    width: 100
  };
  // generate image source
  var src = ips.src(imageData);
  // create and image element
  var img1 = document.createElement("IMG");
  // set the image src attribute
  img1.setAttribute('src', src);
  // append the image to the body
  document.body.appendChild(img1);
  </script>
</body>

Each service supports different placeholder variations. An image data object that contains all types of image variations could include the following attributes.

Attribute	Options	Description
`width`	integer	Width of the image
`height`	integer	Height of the image
`filter`	string	Optional. Image filter (provided by service)
`foreground`	string	Optional. Image foreground/text color
`background`	string	Optional. Image background color
`format`	string	Optional. Image format (gif, jpeg, jpg, png)
`text`	string	Optional. Text displayed in the image
`category`	string	Optional. Image category provided by service
`delay`	integer	Optional. Response delay from server
`brand`	string	Optional. Brand image
`flag`	string	Optional. Flag image
`texture`	string	Optional. Texture applied to backgrounds

Configure

There are several settings that can be applied to the IPS configuration. They include:

var IPS = require('img-placeholder-src');
var ips = new IPS({
  serviceOverride: null,  // override service name          ex: 'placecage'
  service: 'placeholdit', // default service name           ex: 'fillmurray'
  protocol: null          // protocol prepended to src url  ex: 'https'
});

API

src(imageData, service, options)

Accepts an image data object containing at least a height and width. If the optional unique attribute is passed, the image src size will be incremented by the unique value. This should be the index within a list. This forces the image services to send a different image instead of sending the same image if a duplicate size is requested. For example, the output would look like:

var data = [
  {height: 300, width: 300},
  {height: 300, width: 300},
  {height: 300, width: 300}
]
list.forEach(function(item, index) {
  console.log( ips.srcset(data, 'placecage', {unique:index}) );
}
/*
http://placecage.com/300/300 ...
http://placecage.com/301/301 ...
http://placecage.com/302/302 ...
*/

srcset(srcsetData, service, options)

Accepts an array of image data objects and returns a string of comma seperated source references and sizes. Optional options can be passed to the internal src() call.

register(serviceData)

Registers a new image service function.

Attribute	Options	Description
`name`	string	Name of registered placeholder service
`render`	function	`[data]` accepts settings that will populate the image source string which it returns. A template compile function could be used here.
`modifier`	function	Optional. Additional logic to modify data passed to the image template. Accepts a data object and must: return the modifed data object.

ips.register({
  name: 'placekitten',
  render: function(args) {
    return (typeof(args.protocol) !== 'undefined' ? args.protocol : "")
      + '//placekitten.com'
      + (typeof(args.filter) !== 'undefined' ? '/'+args.filter : "")
      + '/' + args.width + '/' + args.width;
  },
  modifier: function(data) {
    return data;
  }
});

var imageData = {
  height: 100,
  width: 100,
  filter: 'greyscale'
};

var src = ips.src(imageData, 'placekitten');
console.log(src);

/*
//placekitten.com/g/100x100
*/

see services.es6.js for modifier example

API - Services

There are shorthand functions for each service. Although, I would recommend to use the base src or srcset functions. Why? In a application you could conditionally override every placeholder src by setting a configuration variable. For example:

var serviceOverride = 'fillmurray';
var ips = new IPS({
  serviceOverride: 'fillmurray'
});

<img src="{{ ips.src(data, 'placeholdit') }}"/>

If serviceOverride is set, all image sources would be replaced with fillmurray sources rather than placeholdit. This allows for quickly changing image sources.

src(imageData, options)

srcset(imageData, options)

Services

By default, these services are supported with no extra configuration. New services can be added by passing a serviceData object to the ips.register function. See the API for reference

Why

Populating actual content for a front-end that will later be integrated into a CMS is a waste of time. Placeholder content is more efficient and there are several image services out there that you can use. My default has always been PLACEHOLD.IT because the file sizes are small, the dimensions are displayed which is helpful for integrators, the image can be customized in a bunch of different ways, and there's no awkward conversation with the client about why Bill Murray is all over their site. The biggest problem with PLACEHOLD.IT is that the image files are so small. They don't accurately represent the final site with actual image content and weight.

As developers, we should always be testing and optimizing our code to be as efficient and accessible as possible. To do that we need more realistic placeholder content. We need to be able to test with actual images while also using simpler placeholder content for client reviews. This would require manually updating image sources which could be very tedious and time consuming, especially if you are using responsive image techniques. Instead, this module makes it possible to define placeholder image attributes like height and width, then generate the service image src and srcset attribute on demand.

Contribute

Clone this repo
Build module and run tests npm run watch

npm test - runs application mocha tests
npm run watch - runs the wepack build and mocha tests. Watches for new changes
npm run build:dev - runs the wepack build
npm run dev - runs the webpack build and tests the application for errors. npm run build - builds various versions of the script to be used on the demo site and by browser