drilldown.js

Safely accesses deep properties of objects.

// npm install drilldown
// bower install drilldown
var dd = require('drilldown');

Strict version locking is recommended during release 0.0.x

Ever run into this?

var foo;
foo.bar;
// TypeError: Cannot read property 'bar' of undefined

You can now check deeply nested properties cleanly!

var foo = {abc: {def: {ghi: 'jkl'}}};
dd(foo)('abc')('def')('ghi').val is 'jkl'
dd(foo)('abc')('zzz')('yyy').val is undefined

// You don't need to use this ugly idiom anymore!
(((foo || {}).abc || {}).def || {}).ghi  // no

Check if a deep property exists:

dd(foo)('abc').exists

Works with arrays too:

var foo = {abc: [ {bar: 'def'},{bar: 'ghi'} ]};
dd(foo)('abc')(0)('bar').val is 'def'

Safely call functions:

var foo = {abc: {addOne: function(x) { return x + 1; }}};
dd(foo)('abc')('addOne').invoke(5); returns 6
dd(foo)('zzz')('aaa').invoke(5); returns undefined

Update values if the original value exists:

var foo = {abc: {def: {ghi: 'jkl'}}};
var newValue = {ping: 'pong'};

dd(foo)('abc')('def').update(newValue);
//  - foo is now {abc: {def: {ping: 'pong'}}}
//  - {ping: 'pong'} is returned

dd(foo)('abc')('zzz').update(5);
//  - foo is unchanged
//  - undefined is returned

Set values even if the path drilled to does not exist:

var foo = {abc: {}};
dd(foo)('abc')('def')('ghi').set('jkl');
//  - foo is now {abc: {def: {ghi: 'jkl}}}

To prevent confusion, only own properties are drilled into.

Available dd properties:

• val - the value
• exists - true if val is defined
• update function(value) - sets the value if the value exists
• set function(value) - sets the value at any path
• invoke - the value if the value is a function, or else a dummy function

Alternatives:

• lodash or underscore: _.get(foo, 'abc.def.ghi')
• nevernull: nn(foo)('abc.def')('ghi').val
• vanilla es5: (((foo || {}).abc || {}).def || {}).ghi

Drilldown works with dots and brackets in property names, which may be useful for drilling with user input.