JavaScript For Loop skips some items in an array

Question

I'm trying to remove all of the items with more than one 'o' from the itCompanies array and then print the array to console. I'm not sure why, but when I'm splitting each item in the array to letters to check if there are more than one 'o', Google and Apple both get skipped.

const itCompanies = ['Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon'];
for (let i = 0; i < itCompanies.length; i++){
    let s = itCompanies[i].split('');
    let count = 0;
    for (let j = 0; j < s.length; j++){
        if (s[j] == 'o' ){
            count++;
        }
    }
    if (count >= 2){
        itCompanies.splice(i, 1);
    }
}
console.log(itCompanies);

Output

Array(5)
0: "Google"
1: "Apple"
2: "IBM"
3: "Oracle"
4: "Amazon"

Wanted Output

Array(5)
0: "Apple"
1: "IBM"
2: "Oracle"
3: "Amazon"

splice changes the index of the actual item. you need to decrement the index with the count of deleted items. — Nina Scholz, Jul 07 '22 at 13:27
@Jashuraku occurence of `o` is sequentially or any where with in `word`. — Mohit Sharma, Jul 07 '22 at 14:01

score 1 · Answer 1 · answered Jul 07 '22 at 13:32

I think it's better to replace the O's and then compare the lengths from the original string vs the string after the replacement.

const itCompanies = ['Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon'];
const result = itCompanies.filter(s => s.length - s.replace(/o/g, "").length < 2);

console.log(result);

The splice has an effect on the indexes because you're mutating the array, you can work around this by looping in a backward direction.

const itCompanies = ['Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon'];
for (let i = itCompanies.length - 1; i >= 0; i--){
    let s = itCompanies[i].split('');
    let count = 0;
    for (let j = 0; j < s.length; j++){
        if (s[j] == 'o' ){
            count++;
        }
    }
    if (count >= 2){
        itCompanies.splice(i, 1);
    }
}
console.log(itCompanies);

Debug Diva · Answer 2 · 2022-07-07T13:54:46.880

0

You can achieve this by using Array.filter() method along with Array.some().

Live Demo :

const itCompanies = ['Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon'];

const res = itCompanies.filter(company => {
    return ![...company].filter((c1, i1, a) => a.some((c2, i2) => {
    if (c1 === 'o') {
        return c1 == c2 && i1 != i2
    }
  })).join('');
});

console.log(res);

edited Jul 07 '22 at 13:54

answered Jul 07 '22 at 13:39

Debug Diva

26,058
13
70
123

score 0 · Answer 3 · answered Jul 07 '22 at 13:40

0

Splice is basically removing the items dynamically, inside the for loop so the index of the items in the array also changes.

answered Jul 07 '22 at 13:40

Ankit Sharma

164
8

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Jul 08 '22 at 20:13

score 0 · Answer 4 · answered Jul 07 '22 at 13:52

Instead of splicing the array, which changes the index , you could move the item, you like to keep into the place of deleted items and change the length at the end.

This approach keeps the same object reference to the array, as in the question.

const
    itCompanies = ['Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon'];

let i = 0, j = 0;
    
while (i < itCompanies.length) {
    if (!(itCompanies[i].match(/o/g)?.length > 1)) {
        itCompanies[j] = itCompanies[i];
        j++;
    }
    i++;
}

itCompanies.length = j;

console.log(itCompanies);

JavaScript For Loop skips some items in an array

4 Answers4