YUI Library Examples: JSON: Adding new object members during parsing

JSON: Adding new object members during parsing

This example shows how to use the reviver parameter in JSON.parse to add new object members and format existing members during the parsing phase.

View example in new window.

Choose a currency, then get the data

Inventory
SKU	Item	Price (USD)	Price (USD)
Click Get Data

The data

The data returned from the server will be a JSON string containing this object structure:

Create a reviver function

We'll contain all the moving parts in an example namespace. In it, we'll include the currency exchange rates and a function to reference the rates to add a new member to the JSON response as it is being parsed.

Sending the request and parsing the JSON response

When the Get Data button is clicked, we send an io request for the JSON data, and in our success handler, pass our conversion function to JSON.parse with the response text. The resulting inventory records will have an additional member, convertedPrice. This data is then passed to a UI method to update the inventory table.

Y.get('#demo_go').on('click', function (e) {
    // Disable the button temporarily
    this.set('disabled',true);

// Store the requested currency
    var sel = Y.get("#demo select");
    example.currency = sel.get("options").item(sel.get("selectedIndex")).get("value");

// Send the request for the JSON data
    Y.io('assets/data.php',{
        timeout : 3000,
        on : {
            success : function (xid, res) {
                var inventory;
                try {
                    inventory = Y.JSON.parse(res.responseText,example.convert);

example.updateTable(inventory);
                }
                catch(e) {
                    alert("Error getting inventory data");
                }
                finally {
                    Y.get('#demo_go').set('disabled',false);
                }
            },
            failure : function () {
                alert("Error getting inventory data");
            }
        }
    });
});

}); // End YUI(..).use(..,function (Y) {

Example markup

Full Code Listing

Below is the full source for the example, including the functions responsible for formatting the price and updating the UI.

YUI({base:"../../build/", timeout: 10000}).use("node", "io", "json-parse",function (Y) {

var example = {
    rates : {"USD":1,"EUR":0.6661,"GBP":0.5207,"AUD":1.1225,"BRL":1.609,"NZD":1.4198,"CAD":1.0667,"CHF":1.0792,"CNY":6.8587 ,"DKK":4.9702,"HKD":7.8064,"INR":42.0168,"JPY":109.8901,"KRW":1000,"LKR":107.5269,"MXN":10.1317,"MYR" :3.3167,"NOK":5.3277,"SEK":6.2617,"SGD":1.4073,"THB":33.7838,"TWD":31.1526,"VEF":2.1445,"ZAR":7.6923 ,"BGN":1.3028,"CZK":16.0514,"EEK":10.4275,"HUF":158.7302,"LTL":2.2999,"LVL":0.4692,"PLN":2.1758,"RON" :2.3804,"SKK":20.2429,"ISK":4.8008,"HRK":81.3008,"RUB":24.3309,"TRY":1.1811,"PHP":44.2478,"COP":2000 ,"ARS":3.1289},

currency : 'USD',

formatCurrency : function (amt) {
        amt += amt % 1 ? "0" : ".00";
        return amt.substr(0,amt.indexOf('.')+3);
    },

convert : function (k,v) {
        // 'this' will refer to the object containing the key:value pair,
        // so this will add a new object member while leaving the original
        // in tact (but formatted to two decimal places).  If the original
        // is not needed, just return the converted value.
        if (k === 'Price') {
            var x = Math.round(v * example.rates[example.currency] * 100) / 100;
            this.convertedPrice = example.formatCurrency(x); // added to item
            return example.formatCurrency(v); // assigned to item.Price
        }
        return v;
    },

updateTable : function () {
        // Update the column header
        Y.get('#demo table th span').set('innerHTML',example.currency);

var tbl   = Y.get('#demo table'),
            html  = ["<tbody>"],i,j = 1,l,item;

if (example.inventory) {
            for (i = 0, l = example.inventory.length; i < l; ++i) {
                item = example.inventory[i];
                html[j++] = '<tr><td>';
                html[j++] = item.SKU;
                html[j++] = '</td><td>';
                html[j++] = item.Item;
                html[j++] = '</td><td>';
                html[j++] = item.Price;
                html[j++] = '</td><td>';
                html[j++] = item.convertedPrice;
                html[j++] = '</td></tr>';
            }
        } else {
            html[j++] = '<tr><td colspan="4">No Inventory data</td></tr>';
        }
        html[j] = "</tbody>";

tbl.replaceChild(Y.Node.create(html.join('')),tbl.query('tbody'));
    }
};

Y.get('#demo_go').on('click', function (e) {
    // Disable the button temporarily
    this.set('disabled',true);

// Store the requested currency
    var sel = Y.get("#demo select");
    example.currency = sel.get("options").item(sel.get("selectedIndex")).get("value");

Y.io('assets/data.php',{
        timeout : 3000,
        on : {
            success : function (xid, res) {
                var inventory;
                try {
                    inventory = Y.JSON.parse(res.responseText,example.convert);

// Expose example objects for inspection
YUI.example = example;
});