使用方法创建javascript对象？

Question

I need to create a "parser" library and want to pass in the source document only one time. How can I supply the source document and store it within the javascript object so I can call methods on the document?

This is what I'm trying, but it feels really messy... especially with the this keyword everywhere:

'use strict';

var reader = function (info) {

    this.doc = info;

    this.getNode = function (name) {
        var nodes = this.doc.items.filter(function (item) {
            return (item.name.toUpperCase() == name.toUpperCase());
        });
        return (nodes.length == 1)
            ? nodes[0]
            : null;
    };

    this.getItems = function (name) {
        var node = this.getNode(name);
        return (node ? node.items : []);
    };

    return this;
};

module.exports = reader;

My goal is to use this reader object in other areas of my app, like this:

var infoDoc = loadFromFile();   // Loads the file from disk

var reader = require('./reader')(infoDoc);

var items = reader('widgets');

Thanks, in advance.

Answer 1

Judging from your usage, you are using the factory pattern. For such a pattern, using this is unnecessary (since in javascript the basic factory pattern isn't constructor based). A simple way to implement it is like:

'use strict';

var reader = function (info) {

    var getNode = function (name) {
        var nodes = info.items.filter(function (item) {
            return (item.name.toUpperCase() == name.toUpperCase());
        });
        return (nodes.length == 1)
            ? nodes[0]
            : null;
    };

    var getItems = function (name) {
        var node = getNode(name);
        return (node ? node.items : []);
    };

    // return a map of the functions you want to expose.
    return {
        getItems: getItems,
        getNode: getNode
    };
};

module.exports = reader;