I have two arrays of objects that represent email addresses that have a label and a value:
var original = [
{
label: 'private',
value: '[email protected]'
},
{
label: 'work',
value: '[email protected]'
}
];
var update = [
{
label: 'private',
value: '[email protected]'
},
{
label: 'school',
value: '[email protected]'
}
];
Now I want to compare and merge the two arrays by the label
field, so that the result would look like this:
var result = [
{
label: 'private',
value: '[email protected]'
},
{
label: 'work',
value: '[email protected]'
},
{
label: 'school',
value: '[email protected]'
}
]
How can I do this e.g. using lodash?
Lodash proves to be much useful when working with arrays, strings, objects etc. It makes math operations and function paradigm much easier, concise. The _. concat() function is used to concatenating the arrays in JavaScript.
assign() method to convert an array of objects to a single object. This merges each object into a single resultant object. The Object. assign() method also merges the properties of one or more objects into a single object.
To merge objects into a new one that has all properties of the merged objects, you have two options: Use a spread operator ( ... ) Use the Object. assign() method.
_.unionBy()
:
This method is like _.union except that it accepts iteratee which is invoked for each element of each arrays to generate the criterion by which uniqueness is computed. Result values are chosen from the first array in which the value occurs.
var original = [
{ label: 'private', value: '[email protected]' },
{ label: 'work', value: '[email protected]' }
];
var update = [
{ label: 'private', value: '[email protected]' },
{ label: 'school', value: '[email protected]' }
];
var result = _.unionBy(update, original, "label");
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>
Convert the lists to objects keyed by label
, merge them by _.assign
, and convert it back to an array. It will even retain order of the items on most browsers.
var original = [
{
label: 'private',
value: '[email protected]'
},
{
label: 'work',
value: '[email protected]'
}
];
var update = [
{
label: 'private',
value: '[email protected]'
},
{
label: 'school',
value: '[email protected]'
}
];
console.log(
_.map(
_.assign(
_.mapKeys(original, v => v.label),
_.mapKeys(update, v => v.label)
)
)
);
// or remove more duplicated code using spread
console.log(
_.map(
_.assign(
...[original, update].map(
coll => _.mapKeys(coll, v => v.label)
)
)
)
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.js"></script>
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