JSFiddle - React, Tailwind, and code Playground

HTML

<input type='button' id='s' value='test' onclick="test()"/>

JavaScript

function test() {

    var arr = ["2:6", "2:3", "1:1", "1:2", "3:1"];
    var resultStr = "";

    for (i = 0; i < arr.length; i++) {

        if (i <= arr.length - 2) {
            var a = arr[i + 1].split(":");
            if (a.length > 0) {
                resultStr += arr[i] + ',' + a[1] + ' | ';
            }
        } else {
            var str = arr[i];
            resultStr += arr[i];
        }
        i++;
    }

    alert(resultStr);
}