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There is _.merge functionality in lodash. I want to achieve the same thing in ES6 or ES7.
Having this snippet:
Object.assign({}, {key: 2}, {key: undefined}) I want to receive {key: 2}. Currently I receive {key: undefined}
This is NOT a deep merge.
Is it possible? If yes then how to achieve that?
237
This is because Object. assign does a shallow merge and not a deep merge. A shallow merge means it will merge properties only at the first level and not the nested level.
The easiest way to merge two objects in JavaScript is with the ES6 spread syntax / operator ( ... ). All you have to do is insert one object into another object along with the spread syntax and any object you use the spread syntax on will be merged into the parent object.
Lodash helps in working with arrays, strings, objects, numbers, etc. The _. merge() method is used to merge two or more objects starting with the left-most to the right-most to create a parent mapping object. When two keys are the same, the generated object will have value for the rightmost key.
The first detail is that merge() copies objects recursively, so _. merge() is a deep copy whereas _. assign() is a shallow copy. The second detail is how merge() handles undefined .
You can't achieve that with a straight usage of Object.assign, because each next object will rewrite the same keys for prev merge. The only way, to filter your incoming objects with some hand-crafted function.
function filterObject(obj) { const ret = {}; Object.keys(obj) .filter((key) => obj[key] !== undefined) .forEach((key) => ret[key] = obj[key]); return ret; } You can simply filter out the keys with undefined values before passing them to Object.assign():
const assign = (target, ...sources) => Object.assign(target, ...sources.map(x => Object.entries(x) .filter(([key, value]) => value !== undefined) .reduce((obj, [key, value]) => (obj[key] = value, obj), {}) )) console.log(assign({}, {key: 2}, {key: undefined}))If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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