Jquery Ajax and Json : How to check if undefined-Collection of common programming errors

2 years ago

admin

2 minutes

I got this Jquery code :

$.ajax({
    url: "?module=gestionApplication&action=getTests&scenario="+encodeURI(scenario)+"&application="+$application,
    dataType:'json',
    success: function( data ) {
        $.each(data, function(i, item) {
            $("#tests tbody").append($tr+"

"+item.ID+"

" + "

"+ "Header : "+item.HEADER + '

' + "Méthode : "+item.METHODE + '

' + "PostBody : "+item.POSTBODY + '

' + "URL : "+item.URL + '

' + "ParseReponse : "+item.PARSEREPONSE + '

' + "

" +

So i got a JSON response from my server, but not all fields are full. Sometimes item.HEADER or item.METHODE can not be defined, so I get “undefined” text in my table. Problem is, I’m French and I would like different text and not this ‘undefined’.

So how can I test if the variable is defined or not? Or even better, is it possible to change this ‘undefined’ text to different text in case the variable is not defined?

You can do a quick conditional / logical-OR check within your concat:
```
"Header : " + (item.HEADER || '') + '
' +
```
so now, if item.HEADER is undefined we will encounter the empty string instead. Of course you could also use a more expressive string like "empty" or whatnot.

if (typeof variable == "undefined")
{
    // variable is undefined
}

Use a ternary operator… ( test ? do if true : do if false )
```
...+( item.HEADER ? item.HEADER : "something french" )+...
```

easily done like so:

if (item.HEADER === undefined) {
    item.HEADER = 'indéfini';
}

// or 

if (typeof item.HEADER === 'undefined') {
    item.HEADER = 'indéfini';
}

Originally posted 2013-11-10 00:10:33.