How to write a function that sorts elements by asc or desc depending on the parameter being called?

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I am a beginner in JavaScript and I am trying to solve a task that I came up. I want to write a function that takes in an array like that:

var array = [{date: '02.01.2017'}, {date: '11.11.2016'}, {date: '12.02.2001'}]

and sorts the array in ascending or descending order depending on the parameter being called with, I have made an attempt, but it doesn't work, how can I create such a function?

What I have tried:

var arr = [{date: '02.01.2017'}, {date: '11.11.2016'}, {date: '12.02.2001'}];

function compare(array, order) {
array.forEach((item) => {
a = item.date.split('.').reverse().join('');
b = item.date.split('.').reverse().join('');

if (order === 'asc') {
if(a > b) {
return 1
}
}
else if(order === 'desc') {
if(a < b) {
return -1
}
}
});
}

compare([{date: '02.01.2017'}, {date: '11.11.2016'}, {date: '12.02.2001'}], 'asc');

Posted 10-Jun-20 8:04am

Member 14859383

Updated 10-Jun-20 9:46am

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2 solutions

Solution 2

The built-in sort method takes a function which is passed two elements from the array and returns a value indicating their relative positions in the sorted list.
Array.prototype.sort() - JavaScript | MDN[^]

You can't pass extra parameters to that function. But you could perhaps use a closure.
Closures - JavaScript | MDN[^]

For example:

JavaScript

function dateComparer(order){
    return function(left, right) {
        var a = left.date.split('.').reverse().join('');
        var b = right.date.split('.').reverse().join('');
        return order === "asc" ? a.localeCompare(b) : b.localeCompare(a);
    };
}

var arr = [ {date: '02.01.2017'}, {date: '11.11.2016'}, {date: '12.02.2001'} ];
arr.sort(dateComparer('desc'));

Posted 10-Jun-20 9:47am

Richard Deeming

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Patrice T · Accepted Answer · 2020-06-10T08:17:00

Quote:
How to write a function that sorts elements by asc or desc depending on the parameter being called?

My easiest is to use or write a sorting function in ascending order. you will find gazillions of algorithms and source code on internet.
And if desc order is requested, reverse order of sorted array by swapping elements of array.