3 Array methods every JavaScript developer should know

Arrays are something all of us come across every day. Today I'll share my picks for 3 of the most uncommonly used Array methods.

isArray

In JavaScript, we have to infer the data type of variables way too often, even more often in nested Objects. One of the ways most JavaScript developers do it (including myself) is to check the length property

const data = { ... }

// true, if arrayKey exists and the arrayKey has a length property
(data?.arrayKey && data.arrayKey.length) 

Although this works, what if I told you there is even a better way to do this?

The Array.isArray(param: any) call checks if the passed value is indeed an array or not and returns a boolean value.

Array.isArray([]); // true
Array.isArray(new Array(22)); // true

Array.isArray(0) // false
Array.isArray({}); // false
Array.isArray(null); // false
Array.isArray(undefined); // false

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For the next two, let's consider a situation

You have to rate some students based on a test as follows

• failed: if all answers were wrong
• passed: if some answers were correct
• excellent: if all answers were correct

some

The Array.some() methods run the provided function on each item of the array and return true, if the provided function returns true for any of them, otherwise false.

So in our scenarios, we can apply Array.some() for the second use case.

function isCorrectAnswer(answer) { 
 // return true if the answer was correct, otherwise false 
}

const answers = [{ ... }]

// didStudentPass will be true, if any of the answers were  // correct
const didStudentPass = answers.some(isCorrectAnswer)

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every

The Array.every() methods run the provided function on each item of the array and return true, if the provided function returns true for all of them, otherwise false.

Array.every() seems like a perfect fit for the other two scenarios.

function isCorrectAnswer(answer) { 
 // returns true if the answer was correct, otherwise false 
}

function isInCorrectAnswer(answer) { 
 // returns true if the answer was wrong, otherwise false 
}

const answers = [{ ... }]

// didStudentFail will be true, if all of the answers were incorrect    

const didStudentFail = answers.every(isInCorrectAnswer)

// didStudentExcel will be true, if all of the answers were correct    

const didStudentExcel = answers.every(isCorrectAnswer)

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That's it for now. I hope you find this article helpful! Should you have any feedback or questions, please feel free to put them in the comments below, I would love to hear and work on them.

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Until next time

Comments

[Hossein Mousavi]

Cool article

[Anshuman Bhardwaj]

thanks @hossein13m , glad it was helpful.

[Patryk Cieszkowski]

both Array.prototype.some, and Array.prototype.every could be replaced with Array.prototype.filter. And I argue - should be.

[Anshuman Bhardwaj]

yes, you're correct. They are an advancement over filter, while filter returns an array they return a boolean. They have a niche purpose as opposed to filter.

[Jackson Kasi]

thank bro :)

[Anshuman Bhardwaj]

glad you liked it, Jackson