SteelToe

Don't shoot yourself in the foot while traversing JavaScript objects.

Get It

$ npm install steeltoe --save

Usage

SteelToe is a tiny JavaScript function that makes it safe to traipse about objects without worrying about whether keys may or may not exist, and whether it's safe to try and look inside of them. It also provides basic autovivification of objects through the set function.

Getting Values

Method #1

var object = { info: { name: { first: 'Jonathan', last: 'Clem' } } }

steelToe(object)('info')('name')('last')();           // 'Clem'
steelToe(object)('info')('features')('hairColor')();  // undefined

Method #2

var object = { info: { name: { first: 'Jonathan', last: 'Clem' } } }

steelToe(object).get('info.name.last');          // 'Clem'
steelToe(object).get('info.features.hairColor'); // undefined

Setting Values

var jonathan = { info: { name: { first: 'Jonathan', last: 'Clem' } } },

steelToe(jonathan).set('info.name.middle', 'Tyler');
steelToe(jonathan).set('info.favorites.movie', 'Harold & Maude');

jonathan.info.name.middle; // Tyler
jonathan.info.favorites.movie; // Harold & Maude

Details

Let's say you've got some deeply nested data in JavaScript objects that you've just parsed from a JSON API response. For each result, you need to do something if there's some sort of data present:

var fatherFirstNames = [];

for (var i = 0; i < families.length; i ++) {
  var first = families[i].father.info.name.first;

  if (first) {
    fatherFirstNames.push(first);
  }
}

// TypeError: 'undefined' is not an object (evaluating 'family.father.info.name.first')

Whoops! You shot yourself in the foot. You got a TypeError because you had no guarantee that the family had a father, or that the father had info present, or that his name was returned! You fix it by writing this monstrosity:

var farherFirstNames = [];

for (var i = 0; i < families.length; i++) {
  var father = families[i].father;

  if (father && father.info && father.info.name && father.info.name.first) {
    fatherFirstNames.push(father.info.name.first);
  }
}

Or, you could use SteelToe and write this:

var fatherFirstNames = [];

for (var i = 0; i < families.length; i++) {
  var name = steelToe(families[i]).get('father.info.name.first');

  if (name) {
    fatherFirstNames.push(name);
  }
}

fatherFirstNames; // ["Hank", "Dale", "Bill"]

The End

SteelToe was made when a coworker of mine said that he wished someone would write a JavaScript library that would allow him to traverse objects without shooting himself in the foot, and that the library was called SteelToe.