Chaining an existing filter inside a custom filter?

Question

I have a custom filter that uses the number filter and a custom partspermillion filter that adds "ppm" at the end. Currently I am chaining my filters, i.e. input | number | partspermillion. However I find this long to type, I want my custom filter to use the number filter everytime. Code as follows:

.filter('partspermillion', function() {
    return function (input) {
        return input + 'ppm';
    }
})

Answer 1

Call your existing filter from new filter using $filter service.

   .filter('partspermillion', function($filter) {
        return function (input) {
            return $filter('number')(input) + 'ppm';
        }
    })