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@ahtcx
Last active June 9, 2024 14:56
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Deep-Merge JavaScript objects with ES6
// ⚠ IMPORTANT: this is old and doesn't work for many different edge cases but I'll keep it as-is for any of you want it
// ⚠ IMPORTANT: you can find more robust versions in the comments or use a library implementation such as lodash's `merge`
// Merge a `source` object to a `target` recursively
const merge = (target, source) => {
// Iterate through `source` properties and if an `Object` set property to merge of `target` and `source` properties
for (const key of Object.keys(source)) {
if (source[key] instanceof Object) Object.assign(source[key], merge(target[key], source[key]))
}
// Join `target` and modified `source`
Object.assign(target || {}, source)
return target
}
const merge=(t,s)=>{const o=Object,a=o.assign;for(const k of o.keys(s))s[k]instanceof o&&a(s[k],merge(t[k],s[k]));return a(t||{},s),t}
@pkit
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pkit commented Apr 18, 2023

@rmp0101

let target = {...existing,...newdata}; This code will be more than enough to merge the data by using javascript.

What part of the word deep you don't understand?

@TacticalSystem
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Very usefull! If someone wants to use more than of two objects you can combine this function with Array.reduce() and an array of objects.
[{}, {}, {}].reduce((ci, ni) => merge(ci, ni), {})

@gavin-lb
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gavin-lb commented Jun 9, 2023

Non-mutating deep merge and copy, making use of the newish structuredClone function for the copying

function deepMerge(target, source) {
  const result = { ...target, ...source };
  for (const key of Object.keys(result)) {
    result[key] =
      typeof target[key] == 'object' && typeof source[key] == 'object'
        ? deepMerge(target[key], source[key])
        : structuredClone(result[key]);
  }
  return result;
}

(some more care would be needed if you need to handle Arrays)

@Pomax
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Pomax commented Jun 30, 2023

note that structuredClone still requires you to do prototype assignment for classed/prototyped objects, though. That doesn't come free.

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