javascript - let in if without braces -

if (true) {   let x = 5 } 

works expected (no syntax error), but

if (true) let x = 5 

throws syntaxerror: unexpected strict mode reserved word in node 4.1.0 , babel

is expected behavior? know stupid example. i'm wondering wether bug or not.

yes expected behavior. the production rule of if statement

 if ( expression[in, ?yield] ) statement[?yield, ?return] 

but let declaration is not statement , therefore not allowed in position:

statement[yield, return] :     blockstatement[?yield, ?return]     variablestatement[?yield]     emptystatement     expressionstatement[?yield]     ifstatement[?yield, ?return]     breakablestatement[?yield, ?return]     continuestatement[?yield]     breakstatement[?yield]     [+return] returnstatement[?yield]     withstatement[?yield, ?return]     labelledstatement[?yield, ?return]     throwstatement[?yield]     trystatement[?yield, ?return]     debuggerstatement  declaration[yield] :     hoistabledeclaration[?yield]     classdeclaration[?yield]     lexicaldeclaration[in, ?yield]  lexicaldeclaration[in, yield] :     letorconst bindinglist[?in, ?yield] ;