JavaScript - removing the same occurences from an array

Question

I have two inputs, one where I choose a letter and one where I say how many of those letter occurrences to splice. Right now I am only able to delete all the occurrences of the letter I select from the input box, but I would like to be able to set how many items of the same letter I can delete.

For example:

I have an array like the one below and I would like to delete only the first "a". If I put 1 in my input, it should do that. If I put 2, then it should delete the first and the second "a" from the array.

It looks easy but I can't come up with a solution to set how many I want them deleted.

var letters = ["a","b","c","a"];

function deleteLetter() {
    var valChosenLetter = document.getElementById("chosen-letter").value;
    var valHowManyToDelete = document.getElementById("how-many-to-delete").value;

    for (var i = letters.length -1; i >= 0; i--) {
        if(letters[i] == valChosenLetter)
        {
            letters.splice(i, 1);
        }
    };
    console.log(letters);
}

I did it manually but that's not the solution:

var letters = ["a","b","c","a"];

function deleteLetter() {
    var valChosenLetter = document.getElementById("chosen-letter").value;
    var valHowManyToDelete = document.getElementById("how-many-to-delete").value;

    for (var i = letters.length -1; i >= 0; i--) {
        if(letters[i] == valChosenLetter)
        {
            if(valHowManyToDelete < 2)
            {
                letters.splice(i, 1);
                break;
            }
            else
            {
                letters.splice(i, 1);
            }
        }
    };
    console.log(letters);
}

score 0 · Answer 1 · answered Sep 02 '15 at 20:19

0

How about something like this:

letters = letters.filter(function (val) {
    if (val === valChosenLetter && howManyToDelete > 0) {
        howManyToDelete -= 1;
        return false;
    }
    return true;
});

So you just reduce howManyToDelete by one each time and just delete as often as it is still positive. Also, you can use filter to make you code a bit more compact.

answered Sep 02 '15 at 20:19

basilikum

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What about `return !(val === valChosenLetter && howManyToDelete--)` – Pavel Gatnar Sep 02 '15 at 20:34

score 0 · Answer 2 · answered Sep 02 '15 at 20:22

This should be able to work:

function deleteLetter( letters, letter, number ) {
    var removed = 0;
    return letters
        .filter(function(char) {
            if ( removed < number && char == letter ) {
                ++removed;
                return false;
            }
            return true;
        })
        .join('');
}

Note: In your provided example, you loop backwards, but your question was to remove the first occurrences, not the last. I followed the question you asked.

JavaScript - removing the same occurences from an array

2 Answers2