Introduction
An array is used to retailer an ordered assortment of values. These values might be a mixture of both the identical knowledge sort or quite a few knowledge varieties – integers, floats, strings, boolean, objects, and plenty extra.
Getting the variety of parts in an array with JavaScript is a typical operation when consuming knowledge or working with APIs in JavaScript. This may be completed both by using the size property or iterating by way of an array and counting the weather.
On this article, we’ll discover ways to get the variety of parts in an array with JavaScript and rather more – the right way to depend distinctive parts and the right way to depend parts of an array based mostly on sure circumstances.
Utilizing the Constructed-in size Property
The usual option to get the overall variety of parts in an array is to make use of the built-in size property:
let myArray = [99, 101.5, "John Doe", true, { age: 44 }];
let whole = myArray.size;
console.log(whole);
let whole = [99, 101.5, "John Doe", true, { age: 44 }].size;
console.log(whole);
Notice: size refers to a cached worth of the size of the array, computed when the array is being created. Subsequently, you do not iterate the array by calling size explicitly, nor implicitly. This ensures that size scales as much as an arbitrary stage and does not affect the efficiency of your utility, such because the affect you’d really feel when manually looping by way of.
Utilizing Loops in JavaScript
JavaScript loops will also be used to depend the size of an array by iterating by way of the array and incrementing the counter variable by one for every component within the array. That is principally used whenever you need to carry out sure operations on the weather themselves or on a selected component since we’re iterating by way of all the weather within the array.
Notice: This strategy tougher in comparison with the beforehand described size property, although, it is fairly easy in and of itself. It is value noting that longer arrays take longer to iterate by way of, whereas size returns the cached worth with a continuing lookup time.
for Loop
let myArray = [99, 101.5, "John Doe", true, { age: 44 }];
let whole = 0;
for (let i = 0; i < myArray.size; i++) {
whole++;
}
console.log(whole);
for…in Loop
let myArray = [99, 101.5, "John Doe", true, { age: 44 }];
let whole = 0;
for (i in myArray) {
whole++;
}
console.log(whole);
Get the Variety of Distinctive Parts in an Array
Arrays in JavaScript can have a number of parts of various knowledge varieties and these parts might embrace some duplicates. If we need to get the variety of distinctive parts we are able to use the Set()constructor.
It creates a set out of the array handed as its argument. Subsequently it helps us take away duplicates and returns solely distinctive parts (a set is a group of distinctive parts). When duplicates are eliminated, we are able to use the size property to get the variety of distinctive parts.
For instance, suppose we now have an array of names that has a complete of seven parts, amongst which 6 are distinctive. We will get the distinctive parts first after which make use of the size property to get the size:
let names = ["John", "Dan", "Jane", "Sam", "Alisa", "John", "Pete"];
let uniqueNames = [...new Set(names)];
let totalPeople = uniqueNames.size;
console.log(totalPeople);
Notice: This may additionally work with loops. After we get the distinctive parts saved in a brand new array, all we now have to do is to loop it by way of and depend parts as we have finished earlier.
What If an Array Incorporates Different Arrays as Parts?
As we have acknowledged earlier than, arrays in JavaScript can comprise parts of many knowledge varieties – together with an Array knowledge sort. This can be a bit complicated at first, however whenever you get a grasp on how size property counts these subarrays, you’re going to have the ability to deal with this example with none issues.
The primary technique that in all probability goes to thoughts is to make use of the size property:
let myArray = [["John", "Pete"], [90, 2], [], [34, 45, 2], [9,4], "John Doe", true, [19]];
let whole = myArray.size;
console.log(whole);
Notice how the size property treats every subarray as one component. It does not take into account the contents of subarrays – irrespective of if it is empty or it has numerous parts, it’s counted as one component of the unique array (on this case, myArray).
Get the Variety of Parts in an Array Containing Different Arrays
Let’s now discover ways to depend the variety of all parts in an array – together with these parts inside subarray parts. We will use a few approaches, similar to a for loop or a for...in, and so on.
We’ll first initialize the totalLength to 0, then create a perform (myLength()) which will probably be used to loop by way of the array and depend the variety of its parts. To start with, we have to loop by way of the unique array and take into account every of its parts. If the component just isn’t an array, we’ll simply enhance the totalLength by 1. Alternatively, if the present component is an array (subarray of the unique array), we’ll recursively name the myLength technique to calculate the variety of its parts:
let myArray = [["John", "Pete"], [90, 2], [], [34, 45, 2], [9,4], "John Doe", true, [19]];
let totalLength = 0;
const myLength = (array) => {
for (let i in array) {
if (Array.isArray(array[i])) {
myLength(array[i]);
} else {
totalLength++;
}
}
};
myLength(myArray);
console.log(totalLength);
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Alternatively, you’ll be able to merely name the flat() technique on myArray, which flattens it by recursively concatenating all the parts right into a 1D array, after which name size on the brand new array:
console.log(myArray.flat().size)
Rely Based mostly on Circumstances
Like we have talked about earlier, we are able to additionally depend the variety of parts in an array based mostly on sure circumstances. For instance, suppose we now have an array of scholars which consists of objects, every object containing college students title and rating:
const college students = [
{ name: "John Doe", score: 70 },
{ name: "Jane Doe", score: 40 },
{ name: "Sarah Jane", score: 33 },
{ name: "John Tough", score: 84 },
{ name: "Jabes Tough", score: 64 }
];
We will depend the overall variety of college students that rating above 60, by looping by way of every component and counting ones that handed the predefined situation:
let whole = 0;
college students.forEach((scholar) => {
if (scholar.rating >= 60) {
whole++;
}
});
console.log(whole);
This is able to additionally work for different iteration strategies just like the for loop:
let whole = 0;
for (let i = 0; i < college students.size; i++) {
if (college students[i].rating >= 60) {
whole++;
}
}
console.log(whole);
Conclusion
On this article, we discovered the right way to get the variety of parts in an array and we noticed numerous situations that might warrant us getting the size of an array and the way we might obtain every of them.
