amilajack / safe-access-check

A micro library that prevents unsafe coercion and property access in javascript

safe-access-check

⚠️ Experimental. Intended to be used by compilers and code checkers ⚠️

Todos

• Existential check of enumerable properties
• Optional logging of values recieved
• Clearer, more consistent error messages

Installation

npm install --save-dev safe-access-check

Usage

import { safeCoerce, safePropertyAccess } from 'safe-access-check';

// ------------------------------------------------
// 1. Usage as an expression
// ------------------------------------------------
let some = moo + '10' // 'moo10'
some = safeCoerce('moo', '+', 10) // 'moo10'

// ------------------------------------------------
// 2. Usage for coercion safeguard
// ------------------------------------------------
[] + {} // "[object Object]"

safeCoerce([], '+', {})
// TypeError: 'Unexpected coercion of type "Object" and
// type "Array" using "+" operator'

NaN + undefined // NaN

safeCoerce(NaN, '+', undefined);
// TypeError: Unexpected coercion of type "NaN" and type
// "undefined" using "+" operator

safeCoerce(new String('12'), '>', 12);
// TypeError: Unexpected comparison of type "String" and type
// "number" using ">" operator

// ------------------------------------------------
// 3. Usage for better undefined propagation errors
// ------------------------------------------------
const obj = {
  foo: {
    bar: {
      baz: false
    }
  }
}

obj.foo.bar._MOO_.baz;
// TypeError: 'Cannot read property 'baz' of undefined'

safePropertyAccess(['foo', 'bar', '_MOO_', 'baz'], obj);
// TypeError: Property "_MOO_" does not exist in "Object.foo._MOO_"

// ------------------------------------------------
// 4. Usage as out of bounds check
// ------------------------------------------------
const obj = {
  woo: ['']
}

obj.woo[1] // undefined

safePropertyAccess(['woo', 1], obj)
// TypeError: '"woo[1]" is out of bounds'

safe-access-check's Issues

Idea: Provide links to errors

Some of the error messages may be confusing to beginners. It would be nice if short url could be added to the output of each error message in order to explain the reason of the error message.

PR: Support for ES6 destructuring

Idea: Log values validated on failure

safePropertyAccess(
  ['foo', 'bar', 'baz'],
  // obj without 'baz'
  {
    'foo': {
      'bar': {}  
    }
  }
)

TypeError: "Object.foo.bar.baz" is not defined' on object:
{
   'foo': {
     'bar': {}  
   }
}