Access Scope in Filters

As covered in Register Filters/Tags, we can access filter arguments directly in filter function like:

// Usage: {{ 1 | add: 2, 3 }}
// Output: 6
engine.registerFilter('add', (initial, arg1, arg2) => initial + arg1 + arg2)

When it comes to stateful filters, for example transform a URL path to full URL, we’ll need to access a origin in current scope:

// Usage: {{ '/index.html' | fullURL }}
// Scope: { origin: "https://liquidjs.com" }
// Output: https://liquidjs.com/index.html

engine.registerFilter('fullURL', function (path) {
    const origin = this.context.get(['origin'])
    return new URL(path, origin).toString() 
})

See this JSFiddle: http://jsfiddle.net/ctj364up/1/

Arrow Functions

this in arrow functions is bound to current JavaScript context, you’ll need to use function(){} instead of ()=>{} syntax to access this.context correctly.