I'm trying to figure out what does the empty {} mean.
var $sb = $sb || {};
Does this mean that varaible $sb's value is either copied to itself or it is a function literal?
full context:
var $sb = $sb || {};
$sb.xxx = function() {
// code
}
Add a comment
|
5 Answers
It's shortcut for
new Object()
So this line
var $sb = $sb || {};
Will check if variable $sb exists and if not create new object and assign it to $sb variable.
So in other way you can write this like:
if( !$sb ) {
var $sb = new Object();
}
Comments
var a = {} is called the object literal notation. It's a faster than var a = new Object() because it needs no scope resolution (ie you could have defined a constructor with the same name and therefor the JavaScript engine must do such a lookup).
The pattern var a = a || {}; is used to avoid replacing a in case you have already defined a. In this pattern, the or-operator: || functions as a coalescing operator. If a is null or undefined it will execute the expression at the right-hand of the statement: {}
Using this pattern ensures you that a will always be defined as an object and, in case it already exist, will not be overwritten.
Comments
It's an object literal. Like:
var obj = { x: 4, y: 2 };
only there are no properties:
var obj = {};
The || operator returns the first operand if it evaluates to a non-falsy value, otherwise it returns the second operand. So the expression $sb || {}; returns the value of $sb if it exists, otherwise it creates a new empty object.
Comments
It is the abbreviation for new Object()
Comments
It's short for:
new Object()
In this case, this means $sb will be set to it's own value, or to a new, empy object in case $sb is undefined.