Remove Duplicate Item From Array Javascript

I'm looking for an easy way of removing a duplicate value from an array. I figured out how to detect if there is a duplicate or not, just I don't know how to 'push' it from the va

Solution 1:

Why do it the hard way, it can be done more easily using javascript filter function which is specifically for this kind of operations:

var arr = ["apple", "bannana", "orange", "apple", "orange"];

arr = arr.filter( function( item, index, inputArray ) {
           return inputArray.indexOf(item) == index;
    });


---------------------
Output: ["apple", "bannana", "orange"]

Solution 2:

Based on user2668376 solution, this will return a new array without duplicates.

Array.prototype.removeDuplicates = function () {
    return this.filter(function (item, index, self) {
        return self.indexOf(item) == index;
    });
};

After that you can do:

[1, 3, 3, 7].removeDuplicates();

Result will be; [1, 3, 7].

Solution 3:

These are the functions I created/use for removing duplicates:

var removeDuplicatesInPlace = function (arr) {
    var i, j, cur, found;
    for (i = arr.length - 1; i >= 0; i--) {
        cur = arr[i];
        found = false;
        for (j = i - 1; !found && j >= 0; j--) {
            if (cur === arr[j]) {
                if (i !== j) {
                    arr.splice(i, 1);
                }
                found = true;
            }
        }
    }
    return arr;
};

var removeDuplicatesGetCopy = function (arr) {
    var ret, len, i, j, cur, found;
    ret = [];
    len = arr.length;
    for (i = 0; i < len; i++) {
        cur = arr[i];
        found = false;
        for (j = 0; !found && (j < len); j++) {
            if (cur === arr[j]) {
                if (i === j) {
                    ret.push(cur);
                }
                found = true;
            }
        }
    }
    return ret;
};

So using the first one, this is how your code could look:

function cleanUp() {
    var text = document.getElementById("fld"),
        textVal = text.value,
        array;

    textVal = textVal.replace(/\r/g, " ");
    array = textVal.split(/\n/g);

    text.value = removeDuplicatesInPlace(array).join("\n");
}

DEMO: http://jsfiddle.net/VrcN6/1/

Solution 4:

You can use Array.reduce() to remove the duplicates. You need a helper object to keep track of how many times an item has been seen.

function cleanUp() 
{
    var textBox = document.getElementById("fld"),
    array = textBox.value.split(/\r?\n/g),
    o = {},
    output;

    output = array.reduce(function(prev, current) {
        var key = '$' + current;

        // have we seen this value before?
        if (o[key] === void 0) {
            prev.push(current);
            o[key] = true;
        }

        return prev;
    }, []);

    // write back the result
    textBox.value = output.join("\n");
}

The output of the reduce() step can be used directly to populate the text area again, without affecting the original sort order.

Demo

Solution 5:

You can do this easily with just an object:

function removeDuplicates(text) {
    var seen = {};
    var result = '';

    for (var i = 0; i < text.length; i++) {
        var char = text.charAt(i);

        if (char in seen) {
            continue;
        } else {
            seen[char] = true;
            result += char;
        }
    }

    return result;
}

function cleanUp() {
    var elem = document.getElementById("fld");

    elem.value = removeDuplicates(elem.value);
}