JSFiddle - React, Tailwind, and code Playground

HTML

<div id="output"></div>

JavaScript

var outputArea = document.getElementById('output');
var output = function(text) {
    outputArea.innerHTML += '<div>' + text + '</div>';
};

var input = [3, 4, 23, 5];

output('"filter" demo');
output('<br\>Input: ' + input);

var filter = function(cb, seq) {
    var ret = [];
    
    for(var i = 0, len = seq.length; i < len; i++) {
        var item = seq[i];
        
        if(cb(item, i)) {
            ret.push(item);
        }
    }
    
    return ret;
}

output('<br\>Retain just items >= 5');
var result = filter(
    function(v) {
        return v >= 5;
    },
    input
);

output('<br\>Result: ' + result);