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

JSON Utility: 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.

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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 the YAHOO.demo.JSONReviver 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 asyncRequest for the JSON data from YUI's Connection Manager. In our success handler, we 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.

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.

YAHOO.util.Event.onDOMReady(function () {

// Set up some shortcuts
var JSON  = YAHOO.lang.JSON,
    Dom   = YAHOO.util.Dom,
    Event = YAHOO.util.Event,
    Demo;

// To avoid a Safari issue with JSON reviver adding properties
JSON.useNativeParse = false;

Demo = YAHOO.namespace('demo').JSONReviver = {
    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 * Demo.rates[Demo.currency] * 100) / 100;
            this.convertedPrice = Demo.formatCurrency(x); // added to item
            return Demo.formatCurrency(v); // assigned to item.Price
        }
        return v;
    },

updateTable : function (inventory) {
        var demo       = Dom.get('demo'),
            tbl        = demo.getElementsByTagName('table')[0],
            tbody      = tbl.getElementsByTagName('tbody')[0],
            col_header = tbl.getElementsByTagName('span')[0],
            tmp        = document.createElement('div'),
            html       = ["<table><tbody>"],i,j = 1,l,item;

// Update the column header
        col_header.innerHTML = Demo.currency;

if (inventory) {
            for (i = 0, l = inventory.length; i < l; ++i) {
                item = 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></table>";

tmp.innerHTML = html.join('');

tbl.replaceChild(tmp.getElementsByTagName('tbody')[0], tbody);
    }
};

Event.on('demo_go','click', function (e) {

var self = this,     // Cache this for the async callback closure
        sel  = Dom.get('currencies'); // Store the requested currency

// Disable the button temporarily
    this.disabled = true;

// Store the requested currency
    Demo.currency = sel.value;

YAHOO.util.Connect.asyncRequest('GET','assets/data.php',{
        timeout : 3000,
        success : function (res) {
            var inventory;
            try {
                inventory = JSON.parse(res.responseText,Demo.convert);

Demo.updateTable(inventory);
            }
            catch(e) {
                alert("Error getting inventory data");
            }
            finally {
                self.disabled = false;
            }
        },
        failure : function () {
            alert("Error getting inventory data");
        }
    });
});

});

YUI Logger Output:

Note: Logging and debugging is currently turned off for this example.

Reload with logging
and debugging enabled.

JSON Utility Examples:

More JSON Utility Resources:

All YUI 2.x users should review the YUI 2.8.2 security bulletin, which discusses a vulnerability present in YUI 2.4.0-2.8.1.