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JavaScript is full of tricks. JavaScript is a huge language with a set of sometimes strange features that make it special and different. There are many ways to get things done in JavaScript; Especially for one of the most important concepts in the programming world, arrays. Today, we’re going to review a series of interesting and useful tricks for using arrays in JavaScript.

Removes duplicates from an array

This is a very popular interview question about Javascript arrays, how to extract unique values from Javascript arrays. Here are two quick and easy solutions to this problem.

👉 : Array. From (new Set(arR)); 👉 : [...new Set(ARR)];Copy the code

Replaces a specific value in an array

Sometimes you need to replace specific values in an array when you create code, and there’s a nice short way to do that, but you may not know it yet.

We can use.splice(start, value to remove,….. , valueToAdd)

  • [start] specifies where we want to start [add/remove] (if negative, from the end of the array)

  • 【value to remove】 Number of items to be removed

  • [….., valueToAdd] and new items added to the array

    Positive 👉arr1.splice(0, 2, "Hi", "good"); Negative 👉arr2.splice(-1, 2, "Hi", "good");Copy the code

If you want to replace a specified value

For example, if we want to replace “ah” with “oh” in the next example, we can do this

Var Arr = [' you ',' ok ',' ah ','!']; Let replaceIndex = arr.indexof (" ah "); If (replaceIndex > -1) {Arr[replaceIndex] = ""; } console.log(Arr)Copy the code

Object to Array

Use the.from() method to quickly convert an object property into an array

var friendsNames = Array.from(friends, ({name}) => name);
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Convert an array into an object

If we have an array and we need to convert it to an object containing the data, we can use the extension operator (…) To do so

var arrObj = { ... arr };Copy the code

Fill the array with data

When we create an array, there are cases where we want to fill it with some data, or we need an array with the same value, in which case the.fill() method provides a simple and clean solution.

var newArray = new Array(5).fill("Axjy");
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Merge array

Do you know how to merge an array into one without using the.concat() method?

An easy way to combine any number of arrays into a single line of code is to use the extension operator (…) .

var arr = [...arr1,...arr2,...arr3]
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Find the intersection of two arrays

This is also one of the most popular challenges you may face in any Javascript interview, as it indicates whether you can use array methods and what your logic is.

To find the intersection of two arrays, we will use the method shown earlier in this article to ensure that the values in the array we are examining are not duplicate;

We will use the.filter and.includes methods. As a result, we get an array of values that exist in both arrays.

var duplicatedValues = [...new Set(numOne)].filter(item => numTwo.includes(item));
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Remove false values from array (*)

First, let’s define false values. In Javascript, false values are false, 0, “”, null,NaN, undefined. We can use the.filter() method to filter these false values.

var trueArr = mixedArr.filter(Boolean);
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Get a random value from an array

Sometimes we need to randomly select a value from an array. To create it in a simple, quick, and short manner and to keep our code clean, we can get a random index number based on the array length.

var ArrItem = Arr[(Math.floor(Math.random() * (Arr.length)))]
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You can also do an encapsulation

Array.prototype.random = function () { return this[Math.floor(Math.random() * this.length)]; } : [1, 2, 19, 769].random()Copy the code

Inversion array

When we need to flip our array, instead of having to go through complicated loops and functions to create it, there’s a simple array method that we can flip our array with just one line of code.

It’s going to change the array

var reversedArrs = Arr.reverse();
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I’m not going to change the way I wrote the array

var reversedArrs = [...Arr].reverse();
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The lastIndexOf () method

In Javascript, there is an interesting way to find the index of the last occurrence of a given element. For example, if our array has duplicate values, we can find out where it was last seen.

var lastIndex = nums.lastIndexOf(5);
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Sum all the values in the array

This is a common question in interviews for Javascript engineers. It can be resolved in a single line of code using the.reduce method

var sum = nums.reduce((x, y) => x + y);
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You can also subtract or multiply all values

var sub  = nums.reduce((x, y) => x - y);
var mul  = nums.reduce((x, y) => x * y);
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Empty array

To empty an array, you can use one of these schemes

  • Direct assignment is null

  • Length is changed to 0

  • Splice method

  • The pop method

    Arr = []

Arr.length = 0;

Arr.splice(0);

while (Arr.length > 0) {
    Arr.pop();
}
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Find the maximum array value

To find the maximum value in an array of numbers, we can do this

let max = Math.max(... numbers);Copy the code

Find the array minimum value

We can use min to find the minimum. We also use the extension operator above. Let’s use another one

let min = Math.min.apply(null, numbers);
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So apply is passing in an array

conclusion

In this article, I’ve shown you 15 tips and tricks that I hope will help you code and keep your code clean and concise. In addition, there are many different tricks worth exploring in Javascript that involve not only arrays but also different data types. If you have a better idea, please leave a comment.

Reference:

13 useful JavaScript array tips and tricks you should know

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