difference between service,factory.provider in angularjs

Question

We are using service,factory and provider in the modules of angularjs.my Question is what is the difference among each other and at what condition they should be used in angularjs.please solve my doubt.

Answer 1

A service is a class. You should provide a service with a constructor function. Angular will only instantiate (new up) one instance of this class. It is a singleton.

angular.module('app', [])
    .service('someService', SomeService);

SomeService.$inejct = ['dependency'];
function SomeService(dependency) {
    this.foo = 'foo'
    // . . .
}
SomeService.prototype.bar = function() {
    return 'bar';
}    

A factory expects the function passed to it to follow the JavaScript factory pattern. This is a function that is not newed up, and returns a unique object. Angular will only call this factory once -- so it too is a singleton.

angular.module('app', [])
    .factory('someFactory', ['dependency', someFactory]);

function someFactory(dependency) {
    return {
        foo: 'foo',
        bar: function() {
            return 'bar';
        } 
    }
}

A provider is a class that allows you to configure a service during the config time

angular.module('myApp', [])
    .provider('someService', SomeServiceProvider);

function SomeServiceProvider() {
    this.foo = 'foo'
    this.bar = 'bar';  
}
SomeServiceProvider.prototype.setFooBar = function(foo, bar) {
    this.foo = foo;
    this.bar = bar;
}
SomeServiceProvider.prototype.$get = function() {
    return new SomeService(this.foo, this.bar);
}

function SomeService(foo, bar) {
    this.foo = foo;
    this._bar = bar;
    // . . .
}
SomeService.prototype.bar = function() {
    return this._bar;
}    

So now in the config portion of a module you can do someServiceProvider.setFooBar('baz', 'buz')