What `body!= body` in Jade template means?

Question

This question is related to using Jade templates with Express.js.

I know that when I write layout.jade that contains:

!!!
html
    body != body
        header
            h1 My header

When I call res.render('index') then my actual template is rendered to beginning of the body.

My question is this: what does != body mean and how Jade/Express use that to determine the placement for my template inside the layout? I know that if I change != body inside another element then the actual view is rendered there instead. Does anyone know where this feature is documented?

Answer 1

I quote, from Jade's documentation/guide:

Code buffered by = is escaped by default for security, however to output unescaped return values you may use !=:

p!= aVarContainingMoreHTML

When using res.render('index') the rendered contents of index.jade (in your case) will be passed as a local variable to your layout file (layout.jade). The local variable is available as body. However, if we simply output the body local variable, it would be escaped (special characters will be encoded). Thus, by using !=, the contents of body will be outputted unescaped.

Check out: http://expressjs.com/guide.html#view-rendering