如何使用 for of loop javascript 返回数组中的元素数？

Question

How do I return the number of elements in an array using for of loop javascript?

I know how I can use a for loop to do this but I was wondering if there is a way to do this with a for of loop. In this case would using a regular for loop be better and or the only way to do this is with a loop?

Regular for loop that prints the number of elements in the array:

 const arr = [1, 2, 3, 4]; function logElementForLoop(arr) { console.log("For Loop"); let elemInArr = 0; for (let i = 0; i < arr.length; i++) { elemInArr = i + 1; } console.log(elemInArr); } logElementForLoop(arr);

Answer 1

I was wondering if there is a way to do this with a for of loop...

Yes, it is possible, simply increment the variable ( elemInArr ) inside the loop:

 const arr = [1, 2, 3, 4]; function logElementForLoop(arr) { console.log("For Loop"); let elemInArr = 0; for (let i of arr) { elemInArr++; } console.log(elemInArr); } logElementForLoop(arr);

Answer 2

I guess you are looking for something like for of or for in loops

let count = 0
for(const item of array) {
  count ++
}
console.log('array contains', count, 'elements')

or

let count = 0
for(const index in array) {
  count ++
}
console.log('array contains', count, 'elements')

Answer 3

You need to add 1 to the count, instead of assigning the index plus one.

 function logElementForLoop(arr) { console.log("For Loop"); let elemInArr = 0; for (let i = 0; i < arr.length; i++) { // add one for each element // elemInArr = elemInArr + 1; // is doing it the long way // elemInArr += 1; // jsut add one, handy for adding different values than one elemInArr++; // standard approach } console.log(elemInArr); } const arr = [1, 2, 3, 4]; logElementForLoop(arr);

Answer 4

Well, if you need to count array elements in for loop..? then

 const arr = [1, 2, 3, 4, 5]; // Counter var let counter = 0; // Count in for loop for(let i = 0; i < arr.length; i++) counter++; // Log console.log(counter);

Answer 5

Using a for of loop

 const arr = [1, 2, 3, 4]; function logElementForLoop(arr) { console.log("For Loop"); let elemInArr = 0; for (let i of arr ) { elemInArr = arr.indexOf(i) + 1; } console.log(elemInArr); } logElementForLoop(arr);

or simply increment elemInArr

 const arr = [1, 2, 3, 4]; function logElementForLoop(arr) { console.log("For Loop"); let elemInArr = 0; for (let i of arr ) { elemInArr++ } console.log(elemInArr); } logElementForLoop(arr)