Odd behaviour of comparison of object literals

Question

I have searched but could not find logic behind following in JavaScript.

When I type in the Chrome console:

{} == null 

it returns

Answer 1

I assume you understand why {} == null throws SyntaxError. Long story short it is because { in the begining starting a block statement not an object literal. You could check the answer here

As of why {} == {} this works.

If you check chromium code that evaluates expressions in console. You could find the following (code)

if (/^\s*\{/.test(text) && /\}\s*$/.test(text))
    text = '(' + text + ')';
executionContext.evaluate(text, "console", !!useCommandLineAPI, false, false, true, printResult);

This code wraps {} == {} code with parentheses making it a valid expression ({} == {}) comparing two empty object literals. Which evaluates to false because objects are compared by reference.

Node repl has the same behaviour src

if (/^\s*\{/.test(code) && /\}\s*$/.test(code)) {
  // It's confusing for `{ a : 1 }` to be interpreted as a block
  // statement rather than an object literal.  So, we first try
  // to wrap it in parentheses, so that it will be interpreted as
  // an expression.
  code = `(${code.trim()})\n`;
  wrappedCmd = true;
}