Question 209795 in Javascript Question posted in
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Javascript – How can I manually count the length of an array?

I’m trying to find length of array without built-in length property. Is this a right way? It is going in infinite loop.

let array = [1, 2, 3, 4, 5];
let i;
let count = 0;

while (array[i] != 'undefined') {
  console.log(array[i]);
  i++
  count++;
}

console.log("length of array is" + count);
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2

Answers


  1. 0

    Your code will result in an infinite loop !!

    Firstly, you have declared i but have not initialized it with a value. This means i will be undefined, and when you use it as an index to access array[i], it will always be undefined, resulting in an infinite loop.

    Secondly, in your while loop condition, you are checking array[i] != 'undefined'. This comparison should be array[i] !== undefined (without the quotes around undefined). The undefined keyword should not be treated as a string in this case.

    let array = [1, 2, 3, 4, 5];
let i = 0;
let count = 0;

while (array[i] !== undefined) {
    console.log(array[i]);
    i++;
    count++;
}

console.log("Length of array is " + count);

    I hope I helped you learn something new today 😉

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  2. 0

    A modern forEach() loop seems simpler here. You don’t need to bother with indexes.

    let array = [1, 2, 3, 4, 5];
let count = 0;

array.forEach(element => {
  count++;
});

console.log("length of array is " + count);
console.log('array.length is', array.length);
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