Kevin Powell - Community•16mo ago

Problem with For Loop

Can someone help me figure out the difference between the function afficher() using for...in vs the for loop? Using for..in the output is correct but with for it's not. am I missing something?

function afficher(tab, n = 10) {
    let output = "";
    for (let i = 0; i < tab.length; i++) {
        if (tab[i] % n == 0) {
            output += "\n";
        }
        output += tab[i] + " ";
    }
    return output;
}

function createArray(nbr, max) {
    let tab = [];
    for(let i = 0; i < nbr; i++) {
        let x = Math.floor(Math.random() * max);
        tab.push(x);
    }
    return tab;
}

let tableau = createArray(6, 10);
console.log(afficher(tableau, 4));

function afficher(tab, n = 10) {
    let output = "";
    for (let i = 0; i < tab.length; i++) {
        if (tab[i] % n == 0) {
            output += "\n";
        }
        output += tab[i] + " ";
    }
    return output;
}

function createArray(nbr, max) {
    let tab = [];
    for(let i = 0; i < nbr; i++) {
        let x = Math.floor(Math.random() * max);
        tab.push(x);
    }
    return tab;
}

let tableau = createArray(6, 10);
console.log(afficher(tableau, 4));

function afficher(tab, n = 10) {
    let output = "";
    for (index in tab) {
        if (index % n == 0) {
            output += "\n";
        }
        output += tab[index] + " ";
    }
    return output;
}

function createArray(nbr, max) {
    let tab = [];
    for(let i = 0; i < nbr; i++) {
        let x = Math.floor(Math.random() * max);
        tab.push(x);
    }
    return tab;
}

let tableau = createArray(6, 10);
console.log(afficher(tableau, 4));

function afficher(tab, n = 10) {
    let output = "";
    for (index in tab) {
        if (index % n == 0) {
            output += "\n";
        }
        output += tab[index] + " ";
    }
    return output;
}

function createArray(nbr, max) {
    let tab = [];
    for(let i = 0; i < nbr; i++) {
        let x = Math.floor(Math.random() * max);
        tab.push(x);
    }
    return tab;
}

let tableau = createArray(6, 10);
console.log(afficher(tableau, 4));

3 Replies

WillsterJohnson•16mo ago

for (index in tab) a for..in loop will yield the index, wheras a for..of loop will get the value. The reason the second block is different is because

for (index in tab) {
  if (index % n == 0) {

for (index in tab) {
  if (index % n == 0) {

Means "if the index of the item modulo n is zero", whereas in the first block;

for (let i = 0; i < tab.length; i++) {
  if (tab[i] % n == 0) {

for (let i = 0; i < tab.length; i++) {
  if (tab[i] % n == 0) {

Means "if the item itself modulo n is zero" To fix the second block, you can use for (const tab of tabs) instead of for..in in short; for..in iterates keys (in an array that's the index) for..of iterates the values (in an array that's the items)

kooliris•16mo ago

Thank you! that was helpful

WillsterJohnson•16mo ago

np!

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Problem with For Loop