CustomError(Error)の継承

custom_error_test.js

var test = require('tape')
test('01', function (t) {
    function MyError (message) {
        if (Error.captureStackTrace) {
            Error.captureStackTrace(this, this.constructor)
        } else {
            this.stack = (new Error).stack || ''
        }
        this.name    = this.constructor.name
        this.message = message || this.name
        return this
    }

    ;(function (MyError) {
        var F = function () {}
        F.prototype = Error.prototype
        MyError.prototype = new F
        MyError.prototype.constructor = MyError
    })(MyError)

    var myError = new MyError('foo')

    t.ok(myError instanceof Error, 'myError instanceof Error')
    t.ok(myError instanceof MyError, 'myError instanceof MyError')
    t.ok(myError.constructor === MyError, 'myError.constructor === MyError')
    t.ok(myError.constructor !== Error, 'myError.constructor !== Error')
    t.ok(myError.toString, myError.toString())

    try {
        throw myError
    } catch (err) {
        t.ok(err, 'can catch myError')
        t.ok(/^MyError.+?foo$/.test(err.toString()), '/^MyError foo$/.test(myError.toString())')
        t.ok(err.stack, 'ok err.stack')
    }

    t.end()
})