无法让String.prototype在工厂工作

Question

So I'm trying to implement a function from an an answer here

String.prototype.supplant = function (o) {
     return this.replace(/{([^{}]*)}/g,
         function (a, b) {
             var r = o[b];
             return typeof r === 'string' || typeof r === 'number' ? r : a;
         }
     );
 };

I've been trying to put this in a factory like this

app.factory('Helpers', function() {
  abc = function (o) {
    return supplant(o);
  }

  abc.prototype.supplant = function (o) {
    return this.replace(/{([^{}]*)}/g,
        function (a, b) {
            var r = o[b];
            return typeof r === 'string' || typeof r === 'number' ? r : a;
        }
    );
  };

return abc;
});

I have used 'Helpers' in my controller, but keep getting errors like "I'm {age} years old!".abc is not a function

I need to access the function abc() just like shown in the answer like

 alert("I'm {age} years old!".supplant({ age: 29 }));
 alert("The {a} says {n}, {n}, {n}!".supplant({ a: 'cow', n: 'moo' }));

Answer 1

You need to understand how things work before copy and paste code by hoping it will magically work...

In the example, the String.prototype is used to extend the default JavaScript String object (whatever surrounded by quotes is a String object), so after the following declaration:

String.prototype.supplant = function (o) {
     return this.replace(/{([^{}]*)}/g,
         function (a, b) {
             var r = o[b];
             return typeof r === 'string' || typeof r === 'number' ? r : a;
         }
     );
 };

all strings in your code can invoke the method supplant() (in addition to the existing ones like toUppercase() , toLowerCase() ...).

What you did in the angular factory is meaningless, you are not extending JavaScript's String object that way, but creating a brand new "type", so obviously by declaring:

"a string".supplant()

the interpreter complains about it since that method does not exist (by default JavaScript's String interface does not implement a method called supplant ).

Anyway, since you are using angular, it already provides services for interpolation: https://docs.angularjs.org/api/ng/service/ $interpolate

So, inject that service in your controllers and use it, in this way:

$interpolate(stringToInterpolate)(contextScopeForInterpolation);