Javascript Closure Fun

closure.js

function buildFunctions() {
    
    var arr = [];
    
    for (i = 0; i < 3; i++) {
        
        arr.push(
            function(number) {
                number = number || 0;
                i = i + number;
                console.log(i);
            }
        )
    }
    
    return arr;
    
}

var fs = buildFunctions();

fs[0]();
fs[1](5);
fs[2]();