Question

I’m building a JavaScript parser and got an error when testing it on jQuery on line 496:

isArray: Array.isArray || function( obj ) {
    return jQuery.type(obj) === "array";
},

I have reduced it down to this:

a = b || function() {}

Is this valid ECMA-262 or is it a feature that has been added since then? Either way, how do I express it in terms of a parser?

My abstract syntax tree for an assignment expression is:

data Assignment
    = CondExpr        CondExpr
    | Assign          LeftExpr AssignOp Assignment 
    | AssignFuncDecl  FuncDecl

This doesn’t support assignments in the above format.

I can explain my AST more if needed. Thanks for any help you can give!

Answer 1

You should look for “ecma bnf”. Here’s one of the links.