Get the description of a ES6 Symbol

问题:

I wonder if there is a nice way to get the descriptions of a Symbol.

For example,

var s = Symbol(5);

The default implementation of the toString will simply print Symbol(5)

I would like to find a way to extract the actual description i.e. 5

回答1:

 String(symbol).slice(7, -1) || null

This works because String(symbol) explicitly coerce the symbol into a string e.g. Symbol('test') gets coerced into "Symbol(test)".

Doing a splicing on the from 7 to -1 does a splicing between the two brackets, thus capturing the description test

Note: that this may not work for object descriptions (e.g. Symbol({test})) as objects gets coerced into "[object Object]"

回答2:

There is no neat way to do this. However, if you have registered a symbol in the global registry, you can use Symbol.keyFor():

var s = Symbol.for(5);
console.log(Symbol.keyFor(s));

回答3:

symbol-description package on npm

Returns description of provided symbol:

const symDesc = require('symbol-description')
symDesc(Symbol('foo')) // foo

It was published by me just now after reading this answer here.