how to grab data within a JSON string
Question
Hi all I am trying to display the words "hello JSON" on my web page but it's displaying the full string { "msg": "Hello JSON." } { "msg": "Hello JSON." } . I know why it is doing that, but how can I get it to display just hello JSON without just plopping it into an html script and using just that?
This is my code:
var http = require('http');
var domain = require('domain');
var root = require('./message'); // do I have to replace root w/ message
var image = require('./image'); // for better readability?
function replyError(res) {
try {
res.writeHead(500);
res.end('Server error.');
} catch (err) {
console.error('Error sending response with code 500.');
}
};
function replyNotFound(res) {
res.writeHead(404);
res.end('not found');
}
function handleRequest(req, res) {
console.log('Handling request for ' + req.url);
if (req.url === '/') {
root.handle(req, res);
}
if (req.url === '/image.png'){
image.handle(req, res);
} else {
replyNotFound(res);
}
}
var server = http.createServer();
server.on('request', function(req, res) {
var d = domain.create();
d.on('error', function(err) {
console.error(req.url, err.message);
replyError(res);
});
d.run(function() { handleRequest(req, res)});
});
server.listen(5000);
then message.js or root (in min var root = require(/message)
var http = require('http');
var body;
exports.handle = function(req, res) {
res.writeHead(200, {
'Content-Type': 'application/json',
'Content-Length': body.length
});
res.end(body);
};
exports.init = function(cb) {
require('fs').readFile('app.html', function(err, data) {
if (err) throw err;
body = data;
cb();
});
}
app.html
<html>
<header><title>This is title</title></header>
<body>
Hello world
<span id="ajaxButton" style="cursor: pointer; text-decoration: underline">
Make a request
</span>
<script type="text/javascript">
(function() {
var httpRequest;
document.getElementById("ajaxButton").onclick = function() { makeRequest('message.js'); };
function makeRequest(url) {
if (window.XMLHttpRequest) { // Mozilla, Safari, ...
httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE
try {
httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e) {
try {
httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e) {}
}
}
if (!httpRequest) {
alert('Giving up :( Cannot create an XMLHTTP instance');
return false;
}
httpRequest.onreadystatechange = alertContents;
httpRequest.open('GET', url);
httpRequest.send(msg);
}
function alertContents() {
if (httpRequest.readyState === 4) {
if (httpRequest.status === 200) {
alert(httpRequest.responseText);
} else {
alert('There was a problem with the request.');
}
}
}
})();
</script>
</body>
</html>
2 answers
solution1
2 2014-02-07 02:21:00
Try changing body = data; to body = data.msg; in you 'message.js' file. This will lookup the value for the key, msg , in the JSON object and assign the result to the body variable.
edit
In your alertContents function, replace:
alert(httpRequest.responseText);
with:
var resData = JSON.parse(httpRequest.ResponseText);
alert(resData.msg);
What this does is parse the JSON response into a Javascript object and then looks up the msg attribute and uses that for the alert.
edit 2
Any time that you need to parse JSON, use JSON.parse(jsonString). It will return a native JavaScript object that you can store in a variable and look up attributes on, as in the example above.
solution2
0 2014-02-07 02:34:04
I cannot see where you're receiving the msg from but at the place where you receive the JSON string just do this.
var jsonResult = receivedData();
if (jsonResult && jsonResult.msg)
{
alert(jsonResult.msg);}
}
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