I wrote the function below to return all keys in an object that match a specific pattern. It seems really round-about because there's no filter function in lodash for objects, when you use it all keys are lost. Is this the only way to filter an objects keys using lodash?
export function keysThatMatch (pattern) {
return (data) => {
let x = _.chain(data)
.mapValues((value, key) => {
return [{
key: key,
value: value
}]
})
.values()
.filter(data => {
return data[0].key.match(pattern)
})
.zipWith(data => {
let tmp = {}
tmp[data[0].key] = data[0].value
return tmp
})
.value()
return _.extend.apply(null, x)
}
}
JavaScript objects don't have a filter() method, you must first turn the object into an array to use array's filter() method. You can use the Object. keys() function to convert the object's keys into an array, and accumulate the filtered keys into a new object using the reduce() function as shown below.
Lodash helps in working with arrays, strings, objects, numbers, etc. The _. pickBy() method is used to return a copy of the object that composed of the object properties predicate returns truthy for. Syntax: _.pickBy( object, predicate )
You can use pickBy
from lodash to do this. (https://lodash.com/docs#pickBy)
This example returns an object with keys that start with 'a'
var object = { 'a': 1, 'b': '2', 'c': 3, 'aa': 5};
o2 = _.pickBy(object, function(v, k) {
return k[0] === 'a';
});
o2 === {"a":1,"aa":5}
I don't think you need lodash for this, I would just use Object.keys
, filter for matches then reduce back down to an object like this (untested, but should work):
export function keysThatMatch (pattern) {
return (data) => {
return Object.keys(data).filter((key) => {
return key.match(pattern);
}).reduce((obj, curKey) => {
obj[curKey] = data[curKey];
return obj;
});
}
}
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