dojo.exists¶
Status: | Draft |
---|---|
Version: | 1.0 |
Available: | since V0.9 |
Contents
Check if all objects in a dot-seperated string object path exist, such as "A.B.C"
.
Introduction¶
dojo.exists
is a convenience function, particularly useful for testing long object paths. It accepts a string as its first parameter, and walks down the path it represents. You can optionally provide a root for the path as a second parameter, otherwise it will use a default value of the global object. Each portion of the ‘.’ delimited string is tested for defined-ness, returning true only if each object exists as defined in the strong.
Usage¶
dojo.exists accepts a string as its first parameter, and the root object as its second parameter, and returns true/false.
1 2 3 4 5 | <script type="text/javascript">
if( dojo.exists("myns.widget.Foo") ){
console.log("myns.widget.Foo exists");
}
</script>
|
The second root
parameter is optional, dojo.exists
will use the value of dojo.global
by default (which is usually the current window
). You can use it to root the path in a different window object, or a particular namespace:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | <script type="text/javascript">
// check if a widget class is available
var widgetType = "form.Button";
var myNamespace = docs;
if( dojo.exists(widgetType, myNamespace) ){
console.log( "There's a docs.form.Button available");
} else if( dojo.exists(widgetType, dijit) ){
console.log( "Dijits form.Button class is available");
} else {
console.log( "No form.Button classes are available");
}
</script>
|