Chrome开发者工具控制台的异常行为

Question

If you type in the console

> new Object() 

Empty js object will appear in the console and it is expected, but if you type

> {}

You get undefined

It is strange. Doesn't it ?

Answer 1

Calling a function with new always results in a value. Now, your second line,

{}

is an empty code block, not an object literal.

Try:

({})

or:

0,{}

The console parses lines you type as statements , not expressions. An open curly brace at the start of a statement is a block delimiter, therefore, and not the start of an object literal. By including other tokens to force the parser into parsing an expression, you can then begin an object literal.