JavaScript eval("{}") return behavior?

Question

According to the ECMA-262 Specification, the following statements return `1`: ``` eval("1;;;;;") eval("1;{}") eval("1;var a;") ``` Ensuring that: The value of a StatementList is the value of the last value producing Statement in the StatementList. Can you explain these different returns ? ``` eval("{}") // undefined eval("var a={}; a;") // {} eval("var a={};") // undefined ``` What is the difference between `1;` and `{};` ?

Accepted Answer

Left alone, `{}` is interpreted as a block, not an object. It contains no statements, so does not affect the value of, say, `eval("1;{}")`. To force it to be interpreted as an object, you can use parentheses:

```
eval("1;({})"); // {}
```

JavaScript eval("{}") return behavior?

Solution

Problem