nothrow v1.0.1

nothrow

Encapsulates typesafe deep object/array access.

The nothrow-mentality is based on the fact, that any kind of input (data which is not created from our application) should be considered evil. 99% of the time the interface might be compatible to a naive implementation, but there is remaining risk of our application to terminate unexpectedly.

    // evil
    configService.setName(uncheckedServerData.configuration.name);

    // better, but boilerplate code
    configService.setName(
        uncheckedServerData
        && uncheckedServerData.configuration
        && uncheckedServerData.configuration.name
    );
    
    // nothrow approach
    configService.setName(nothrow(() => uncheckedServerData.configuration.name));

Accessing deep structures problem

Expect that our application state has an array with persons and we want the name of the first person. We could write

    return state.persons[0].name;

and run into danger that either the array is empty and there is no first person

Uncaught TypeError: Cannot read property 'name' of undefined

or the person array has not yet been initialized

Uncaught TypeError: Cannot read property '0' of undefined

or there is actually no state at all

Uncaught TypeError: Cannot read property 'peoples' of undefined

which forces us to write complex checks as conditional access

    return state && state.persons && state.persons[0] && state.persons[0].name;

or 'early return'

    if(!state)
        return undefined;
    
    if(!state.persons)
        return undefined;
    
    if(!state.persons[0])
        return undefined;
    
    return state.persons[0].name;

(other) Solutions

lodash's get function?

    return _.get(state, 'persons[0].name');

Works, but 1. typesafetyness is gone 2. refactoring impossible

the nothrow way

We access structures via accessor function and nothrow guarantees that no exception is thrown, no matter if you're accessing null or undefined via index or calling any non-existing functions.

    import {nothrow} from 'nothrow';
    
    // returns undefined
    return nothrow(() => state.people[0].name);