Don't shoot yourself in the foot traversing objects.
MIT License
Don't shoot yourself in the foot while traversing JavaScript objects.
$ npm install steeltoe --save
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.
var object = { info: { name: { first: 'Jonathan', last: 'Clem' } } }
steelToe(object)('info')('name')('last')(); // 'Clem'
steelToe(object)('info')('features')('hairColor')(); // undefined
var object = { info: { name: { first: 'Jonathan', last: 'Clem' } } }
steelToe(object).get('info.name.last'); // 'Clem'
steelToe(object).get('info.features.hairColor'); // undefined
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
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"]
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.