Typeof arr // 'object' // Assign to a non-numeric propertyĪrr = arr // true, JavaScript arrays are just special objectsģ of the 4 looping constructs ignore the non-numeric property. That means you can add string properties to your array, With for and for/in, you need to print out arr: for ( let i = 0 i console.log(v)) For example, suppose you want to print out the values stored in the below array: const arr = The for and for/in looping constructs give you access to the index in the array, not the actual element. Then you will be able to select the desired array element with something like arr i. You define a variable like i in for (let i in arr), and in each iteration, the variable i will become equal to a key in arr. It is among the most used and straightforward methods for iterating over objects. I'll also link to the relevant ESLint rules that you can use to enforce looping best practices in your projects. The for.in loops through the properties of an object. ![]() I'll provide an overview of the difference between these looping constructs using several different edge cases. In this article, I'll describe the differences between iterating over an array with the 4 primary looping constructs: Some style guides go so far as to ban certain looping constructs. ![]() Tradeoffs are a common cause of confusion. ![]() There's numerous ways to loop over arrays and objects in JavaScript, and the
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