Prevent object constructor being run as function
function Foo() {
if (! (this instanceof Foo)) {
throw "Attempted to call a constructor as a function. " +
"Must use 'new' eg 'new Foo()'.";
}
// ...
}Gives an explanation on console and stops unintended behaviour before it happens.
Written by David Godfrey
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4 Responses
Great point. How about warning and redirecting to new Foo() instead of throwing an exception?
function Foo() {
// verify the new operator was used to
// ensure 'this' works as expected
if (false === (this instanceof Foo)) {
console.warn('Foo() invoked as a function;',
'use `new Foo()` instead');
return new Foo(arguments);
}
// ...
}
Good idea. I'm building new things at the moment, so I wanted other coders to know if they're doing something wrong before it can become a bug later, but if you're adding into existing code it'd make sense to be a warning rather than crash the entire suite. Thanks :)
Perfect, simple and easily implemented on existing code.
Isn't this essentially describing a singleton pattern? http://addyosmani.com/resources/essentialjsdesignpatterns/book/#singletonpatternjavascript
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