JSFiddle - React, Tailwind, and code Playground

JavaScript

var VM = function () {
    var self = this;
    self.arr1 = [1, 2, 3];
    //self.arr2;
 ko.utils.arrayFirst(self.arr1, function (item) {
        if(item == '3')
        {
        alert("test");
        }
        else
        {
        alert("test1");
        }
    });
}
myVM = new VM();
ko.applyBindings(myVM);