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I'm trying to learn javascript by following a tutorial on youtube, and I found this segment of code.
I understand what filter generally does or at least its purpose, but I don't know anything about filter conditions what they do exactly? Any explanation will be appreciated.
setFilteredProducts(
products.filter((item) =>
Object.entries(filters).every(([key, value]) =>
item[key].includes(value)
)
)
);
.entries(filters)
basically returns an array iterator object which is then being iterated using
.every(([key, value])
This is basically creating an iterator(entries) and iterating(every) through it.
Finally, .includes(value) checks if the value is present in item[key]. It is basically a function to search for an element.
Hope it helps!
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Im working with javascript but maybe there is also an general answer.
Assuming we have 10 objects with ids.
Would it be faster to search for an object with an specific id by using the array find() methode:
const found = entries.find(entries => entries.id === myId)
or initial collect the data in a Map and use the get() methode?
Thanks to the comments I know now:
Array.find() is similar iterating/looping through an array and that means, it is slower then using get(), which is not a loop.
So if I want to search only one time in this array, find() should be enough. If I want to find multiple elements in that array. It makes sense to generate a Map from that array.
PS: The amount of 10 was an example. I just wanted to know what generally is faster.
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I'm new to JavaScript and I got this awkward doubt when I went through the concepts of objects in JavaScript, since the disadvantage of arrays in most of the programming languages is that it can hold only homogeneous datatypes. But that is not the case in JS. So why not we use arrays instead of objects in JS?
Array should be used when you have to access values a specific order or want looping through , if you don't care about the key name go with array or if you are concerned with value should be accessed with string key then objects are best .
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I have an object
[{"displayName":"group1"},{"displayName":"group2"}]
I would like to change this to
[{"displayName":["group1","group2"]}]
I searched questions similar to this, however, I don't get the logic.
Any explanation would be appreciated.
Thanks.
Object.assign({}, [{"displayName":"group1"},{"displayName":"group2"}]);
Here, this will produce the result for you, but I think you may want to consider the use of the output first.
let sourceArr = [{"displayName":"group1"},{"displayName":"group2"}]
let targetArr = [{"displayName": sourceArr.map(s => s["displayName"])}];
console.log(targetArr);
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let index = $scope.fetchPanelAssessorDetails.findIndex
( assessor => assessor.name === assessorDet.name );
I tried fetching the index of the object using above code. It worked too, but it affects my minification and uglification of code using grunt. What is the solution to overcome this.
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In the above i attached my database image (front-end). i want to fetch those data as arrays in javascript also need to show it by using documet.write() method.
Thank you in advance.
You provided so little context so I'm gonna make some assumptions on my side.
First I'd like to assume you have to the fetch api. We'll be using that to fetch the data, I'm gonna assume too that you have access to ES6 features and are familiar with promises. And finally, I'm assuming that the data returned is in JSON format.
Here's the solution:
window.fetch('<insert-url-here>')
.then(response => reponse.json())
.then(data => data.forEach(d => document.write(d));