I apologize for the title. I'm not really sure how to best word this as I'm still learning Javascript.
I have an object of dates that have an occurence of dynamic values as follows: (Key = date, value = number)
2021-12-23: 4
2021-12-24: 7
2021-12-27: 6
2022-01-05: 5
... etc
I also have another object that looks something like this:
2022-01-05: 5
Basically, I need the second object to populate 0 for all non-matching keys. For example, the second object would need to look as follows (where the value of the match does not matter):
2021-12-23: 0
2021-12-24: 0
202-12-27: 0
2022-01-05: 5
I'm really stumped on this one, any javascript help would be immensely appreciated.
Here's an implementation using Object.entries and Array.prototype.reduce but there are actually a lot of way to approach this.
const original = {
"2021-12-23": 4,
"2021-12-24": 7,
"2021-12-27": 6,
"2022-01-05": 5
}
function filterObjectByKey( o, key ){
return Object.entries(o).reduce((acc, [k,v])=>{
acc[k] = ( k === key ) ? v : 0;
return acc;
}, {});
}
const filtered = filterObjectByKey( original, "2022-01-05");
console.log( filtered );Updated: The function can also accept the secondary object as an argument and filter based on its keys:
const original = {
"2021-12-23": 4,
"2021-12-24": 7,
"2021-12-27": 6,
"2022-01-05": 5
}
const secondary = {
"2022-01-05": 5
}
function filterObjectByKey( o, sec ){
const keys = Object.keys(sec);
return Object.entries(o).reduce((acc, [k,v])=>{
acc[k] = keys.includes(k) ? v : 0;
return acc;
}, {});
}
const filtered = filterObjectByKey( original, secondary );
console.log( filtered );Perhaps you could use some form of iteration with coalescing operator (||)...
someObjArray.forEach(function(x) {
return {
// if the obj does not have key/value pair for that date, it will use 0 (the value to the right of ||)
2021-12-23: (x['2021-12-23'] || 0),
2021-12-24: (x['2021-12-24'] || 0),
2021-12-27: (x['2021-12-27'] || 0),
2022-01-05: (x['2021-01-05'] || 0)
}
});
OK so what you want to do in order to achieve this is loop through all the keys of the first object (the one with the several DateString keys/Number values) and set the new numeric value to be 0 if that key is not included in the second object.
From your description:
const firstObject = {
2021-12-23: 4,
2021-12-24: 7,
2021-12-27: 6,
2022-01-05: 5
}
const secondObject = {
2022-01-05: 5
}
seems like the code here would benefit from Object.entries which is a function that you can run on an object Object.entries(myObject || {}) and it will return a 2-d array of the Object's [[key, val], [key, val]].
So your final code will look like:
const mapTo0s = (firstObject, secondObject) => {
return Object.fromEntries(Object.entries(firstObject).map(([dateString, value]) => {
if (!secondObject[dateString]) {
return [dateString, 0];
}
return [dateString, value]; // assumes you want to keep the value as is when the secondObject has the value.
}))
};
Object.fromEntries is another javascript method which converts a 2-d array of arrays to an object with corresponding keys. So if you send in [['05-10-2021', 3]] it will return {'05-10-2021': 3 }.
You can run that function like this:
const result = mapTo0s(firstObject, secondObject)
// should result in:
console.log({ result })
/* { result: {
2021-12-23: 0,
2021-12-24: 0,
202-12-27: 0,
2022-01-05: 5
}
}
*/