问题
In the chromium console I run {} === {} and I get a Syntax error, unexpected '==='.
If I however wrap this in parens, like ({} === {}) then I get false, what I'd expect.
Is an object literal, in the first position, confused with a code block or something?
回答1:
Without a surrounding parenthesis, {} would be considered as an empty code block in javascript. = followed by a code block would be an invalid syntax. That is why you are seeing an error there.
If you wrap it inside of a parenthesis like ({} === {}), then it would be considered as an expression and it will be evaluated to false as both are referencing two different objects.
The following example may give you a clear picture about it,
{ var x = 5; console.log(x); } == 2
// will throw the same error that you are facing.
来源：https://stackoverflow.com/questions/35812616/why-do-i-get-a-syntax-error-if-i-run-this-in-the-console