CODEWITHSUNDEEP
javascriptecmascript-6symbols
Hitesh Kumar
Hitesh Kumar

Reputation: 3698

ES6: Why Symbol can not have another symbol as description?

I am learning Es6: Symbols. I am playing with it and trying to create a symbol using another symbol as description:

var s = Symbol('foo');
console.log(s.toString()); //"Symbol(foo)"
var sS = Symbol(s); // <- thorws error
var sF = Symbol.for(s); // <- thorws error
console.log(s, sA);

I am not able to understand why is it not letting me use existing symbol as description. When I run the code above I see following console error:

Uncaught TypeError: Cannot convert a Symbol value to a string
    at Function.for (native)

As the error says that it can not convert the symbol to string. But as you see in code(line 2), by using toString() function I am able to convert the symbol in string. Can anyone please elaborate what's going on? Thanks.

Upvotes: 2

Views: 110

Answers (1)

Bergi
Bergi

Reputation: 664444

why is it not letting me use existing symbol as description

Simply because all descriptions must be strings, nothing else.

the error says that it can not convert the symbol to string, but by using toString() I am able to convert the symbol in string

Yes, you can explicitly cast a symbol to a string and get its description by using the toString method. But all implicit conversions throw exceptions - this is a deliberate feature to prevent us from accidentally using the non-unique description instead of the symbol, e.g. when doing string concatenation with a property key.

Upvotes: 4

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