erkiesken/node-repl-inspect-customInspect.md

## node-repl-inspect-customInspect.md

      
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              node-repl-inspect-customInspect.md
            
          
    When objects implement inspect method but its not meant for inspection then problems might occur.
For example with rxjs package:
> Rx = require("rxjs/Rx")
{ Subject: { [Function: Subject] create: [Function] },
  Observable:
…

> s = new Rx.Subject()
RangeError: Maximum call stack size exceeded
    at Subject.Observable (./node_modules/rxjs/Observable.js:21:24)
    at new Subject (./node_modules/rxjs/Subject.js:17:16)
    at Subject.lift (./node_modules/rxjs/Subject.js:28:23)

This is because Node's util.inspect will try to call s.inspect but that will recurse and throw an error.
Fix is to disable customInspect option for util.inspect as so:
let util = require("util");
let origInspect = util.inspect;
util.inspect = obj => origInspect(obj, { customInspect: false })

Now the same thing as above won't throw:
> s = new Rx.Subject()
Subject {
  _isScalar: false,
  destination: undefined,
…

The customInspect option is documented here.