• The .prop() method gets the property value for only the first element in the matched set.

• $( elem ).prop( "checked" ) true (Boolean) Will change with checkbox state

• $( elem ).attr( "checked" ) (1.6+) "checked" (String) Initial state of the checkbox; does not change

According to the W3C forms specification, the checked attribute is a boolean attribute, which means the corresponding property is true if the attribute is present at all—even if, for example, the attribute has no value or is set to empty string value or even "false". This is true of all boolean attributes.

var foo = 'hello'; (function(f) { var foo = f || 'world'; console.log(foo); })(foo);