I'm building a widget which would be used in different eCommerce sites.

As i'm using underscorejs library, i need to see if underscorejs exists in the parent site and if so what version.

If underscore is already defined in the site and if the version matches with the one i used. I would inturn use their own defined underscore and not make a CDN call to load underscorejs for my widget.

I'm building a widget which would be used in different eCommerce sites.

As i'm using underscorejs library, i need to see if underscorejs exists in the parent site and if so what version.

If underscore is already defined in the site and if the version matches with the one i used. I would inturn use their own defined underscore and not make a CDN call to load underscorejs for my widget.

• javascript
• underscore.js

3 Answers 3

You can easily check that with the following

if (!window._ || window._.VERSION !== '1.7.0') {
  // Load underscore from CDN
}

Get the version of underscorejs used

Check the library itself. Most likely it retained the copyright ment on top of the file.

i need to see if underscorejs exists in the parent site

_.VERSION

You can use this pattern to load library from HTML:

<script>
    (window._ && window._.VERSION === '1.7.0') || document.write("<script src='//cdnjs.cloudflare./ajax/libs/underscore.js/1.7.0/underscore-min.js'>\x3C/script>");
</script>

You can put this script at the beginning to the widget HTML.