README
🌊 defu
Assign default properties, recursively. Lightweight and Fast!
Install
Install package:
yarn add defu
# or
npm install defu
Usage
const options = defu (object, ...defaults)
Leftmost arguments have more priority when assigning defaults.
Arguments
- object (Object): The destination object.
- source (Object): The source object.
const defu = require('defu')
console.log(defu({ 'a': { 'b': 2 } }, { 'a': { 'b': 1, 'c': 3 } }))
// => { a: { b: 2, c: 3 } }
Custom Merger
Sometimes default merging strategy is not desirable. Using defu.extend
we can create a custom instance with different merging strategy.
This function accepts obj
(source object), key
and value
(current value) and should return true
if applied custom merging.
Example: Sum numbers instead of overriding
const ext = defu.extend((obj, key, value) => {
if (typeof obj[key] === 'number' && typeof value === 'number') {
obj[key] += val
return true
}
})
ext({ cost: 15 }, { cost: 10 }) // { cost: 25 }
Function Merger
Using defu.fn
, if user provided a function, it will be called with default value instead of merging.
I can be useful for default values manipulation.
Example: Filter some items from defaults (array) and add 20 to the count default value.
defu.fn({
ignore: (val) => val.filter(item => item !== 'dist'),
count: (count) => count + 20
}, {
ignore: ['node_modules','dist'],
count: 10
})
/*
{
ignore: ['node_modules'],
count: 30
}
*/
Note: if the default value is not defined, the function defined won't be called and kept as value.
Array Function Merger
defu.arrayFn
is similar to defu.fn
but only applies to array values defined in defaults.
Example: Filter some items from defaults (array) and add 20 to the count default value.
defu.arrayFn({
ignore(val) => val.filter(i => i !== 'dist'),
count: () => 20
}, {
ignore: [
'node_modules',
'dist'
],
count: 10
})
/*
{
ignore: ['node_modules'],
count: () => 20
}
*/
Note: the function is called only if the value defined in defaults is an aray.
Remarks
object
anddefaults
are not modified- Nullish values (
null
andundefined
) are skipped. Please use defaults-deep or omit-deep or lodash.defaultsdeep if you need to preserve or different behavior. - Assignment of
__proto__
andconstructor
keys will be skipped to prevent security issues with object pollution. - Will concat
array
values (if default property is defined)
console.log(defu({ array: ['b', 'c'] }, { array: ['a'] }))
// => { array: ['a', 'b', 'c']}
License
MIT. Made with 💖