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Immutable object update
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// Based on 'Easy immutable objects in Javascript' | |
// https://spapas.github.io/2018/04/05/easy-immutable-objects/ | |
const immutable_update = (obj, path, val) => { | |
if (!val) { | |
return path.reduce((obj, [path, val]) => immutable_update(obj, path, val), obj); | |
} | |
let parts = (typeof path === 'string' || path instanceof String) ? path.split('.') : path; | |
const cset = (obj, cidx, val) => { | |
let newval = val; | |
if (typeof val === "function") { | |
newval = val(obj[cidx]); | |
} | |
if (Array.isArray(obj)) { | |
return [...obj.slice(0, cidx * 1), newval, ...obj.slice(cidx * 1 + 1)]; | |
} else { | |
return { ...obj, [cidx]: newval }; | |
} | |
}; | |
let pidx = parts[0]; | |
if(parts.length == 1) { | |
return cset(obj, pidx, val); | |
} else { | |
let remaining = parts.slice(1); | |
return cset(obj, pidx, immutable_update(obj[pidx], remaining, val)); | |
} | |
}; | |
const state = { | |
'users': { | |
'results': [ | |
{'name': 'Sera', 'groups': ['g1', 'g2', 'g3']}, | |
{'name': 'John', 'groups': ['g1', 'g2', 'g3']}, | |
{'name': 'Joe', 'groups': []} | |
], | |
'pagination': { | |
'total': 100, | |
'perpage': 5, | |
'number': 0 | |
} | |
}, | |
'groups': { | |
'results': [], | |
'total': 0 | |
} | |
}; | |
const path_and_value_list = [ | |
['users.results.2.groups.0', 'aa'], | |
['users.results.0.name', (x) => x.toUpperCase()], | |
['users.pagination.total', (x) => x + 1], | |
['users.results.1.name', 'Jack'] | |
]; | |
console.log(state); | |
console.log(immutable_update(state, path_and_value_list)); |
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