Looking to append a count to duplicate entries within a string array. The array in question contains duplicates, as shown below.
var myarray = ["John", "John", "John", "Doe", "Doe", "Smith",
"John", "Doe", "Joe"];
The desired output should be:
var newArray = ["John - 1", "John - 2", "John - 3", "Doe - 1",
"Doe - 2", "Smith", "John - 4", "Doe - 3", "Joe"];
Seeking the most efficient method to achieve this transformation.
Here is a solution that involves utilizing two iterations of Array.map():
var map = {};
var count = myarray.map(function(val) {
return map[val] = (typeof map[val] === "undefined") ? 1 : map[val] + 1;
});
var newArray = myarray.map(function(val, index) {
if (map[val] === 1) {
return val;
} else {
return val + ' - ' + count[index];
}
});
In the first iteration, each unique item's frequency is calculated and stored in an object, creating an array with current frequencies of items.
The second iteration adds the frequency count to items that appear more than once.
For a demonstration, see http://jsfiddle.net/alnitak/Z4dgr/
similar to this
let occurrences = {}, freshArray = [];
// first run, count occurrences
for (let index = 0; index < givenArray.length; index++) {
let element = givenArray[index],
currentCount = occurrences.element;
if (!currentCount) {
currentCount = 1;
} else {
currentCount++;
}
occurrences[element] = currentCount;
element = element + " - " + currentCount;
freshArray.push(element);
}
// Revert changes for elements that occur only once
for (let index = 0; index < givenArray.length; index++) {
let element = givenArray[index],
currentCount = occurrences.element;
if (currentCount === 1) {
freshArray[index] = element;
}
}
Note that I chose to use straightforward javascript for clarity and ease of understanding. Keep in mind that looping through the array twice may not be efficient for large datasets.
This code snippet has not been tested, but a similar approach should yield the desired results.
Here is a script that calculates the count of duplicate values in an array:
var myarray = ["John", "John", "John", "Doe", "Doe", "Smith",
"John", "Doe", "Joe"];
var values = {}, newArray = [];
for (var i = 0; i < myarray.length; i++) {
if (typeof values[myarray[i]] === 'undefined') {
values[myarray[i]] = 1;
} else {
values[myarray[i]] += 1;
}
}
for (var i = 0; i < myarray.length; i++) {
if (values[myarray[i]] > 1) {
newArray.push(myarray[i] + ' - ' + values[myarray[i]]);
} else {
newArray.push(myarray[i]);
}
}
Thank you for considering this solution!
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