why this syntax not producing Error {age:15}toString() in javascript

Try this syntax in console

 {age:15}toString()  
 '[object Undefined]' // this is the return

why this happens it looks syntactically wrong so I’m not sure how the interpreter parse it ?

the object {age:15} looks like completely ignored ? is that true ?

if not ignored dose it mean it garbage as soon as it created I’m just thinking but not sure

>Solution :

{age:15}:

1. Is a block. It is not an object. For more information see What is the explanation for these bizarre JavaScript behaviours mentioned in the 'Wat' talk for CodeMash 2012? and in particular the explanations for {} + [] and {} + {} that deal with the same block behaviour.
2. It contains a label with identifier age which is then followed by the expression-statement 15. For more see What does the JavaScript syntax foo: mean?
3. It is irrelevant to the rest of the code.

The actual output here is only from toString():

console.log(toString());

With that in mind let’s examine the output: toString() is a method on the object prototype. Thus pretty much all objects have it. Including window:

console.log("toString" in window); //true

Calling just toString() means the method will be picked up from the global object – window.

Because the value of this is determined at call time and implicitly there is no object to pick it from:

A normal call would look like someObject.toString() which will set the this value to someObject. It is also equivalent to calling Object.prototype.toString.call(someObject) which will explicitly set the value of this to `someObject.

However with the entire toString() is basically equivalent to Object.prototype.toString.call(undefined) as there is nothing the method is called on.

console.log(Object.prototype.toString.call(undefined))