On Saturday, 9 April 2011 02:46:58 UTC-3, planon wrote:
>
> I was reading Ben Cherry's blog post on Writing Testable Javascript
> and I came across this example:
>
> function Templater() {
> this._templates = {};
> }
>
> Template.prototype = {
> _supplant: function(str, params) {
> for (var prop in params) {
> str.split("{" + prop +"}").join(params[prop]);
> }
> return str;
> },
> render: function(name, params) {
> if (typeof this._templates[name] !== "string") {
> throw "Template " + name + " not found!";
> }
>
> return this._supplant(this._templates[name], params);
> },
> defineTemplate: function(name, template) {
> this._templates[name] = template;
> }
> };
>
>
>
> http://www.adequatelygood.com/2010/7/Writing-Testable-JavaScript
>
>
> My question is why does he use prototype to extend this function
> rather than writing it as:
>
> function Templater(){
> return {
> _supplant:function(){}
>
> etc...
> }
> }
>
> What is the use case for prototype-based extension?
>
I always ask myself when do I really need the Java-like approach in
Javascript, such as using a constructor function and the 'new' operator, and
I don't find a reasonable answer to go about writing code in that way.
In your case, I would use a globally available object instead of a
constructor function:
var Templater = {
templates: {},
supplant: function (str, params) {
var prop;
if (Object.prototype.hasOwnProperty) { // all browsers except Safari 2
for (prop in params) {
if (params.hasOwnProperty(prop)) {
str.split("{" + prop + "}").join(params[prop]);
}
}
}
return str;
},
render: function (name, params) {
if (typeof this.templates[name] !== "string") {
throw "Template " + name + " not found!";
}
return this.supplant(this.templates[name], params);
},
defineTemplate: function (name, template) {
this.templates[name] = template;
}
};
--
JR
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