var a=[{n:1},{n:4},{n:9}]

    while(a.length){
        var e=a.pop();
        console.log(e.n);
    }

    while(a.length){
        if(a.length){
            var e=a.pop();
            console.log(e.n);
        }
    }

    if(a.length){
        var e=a.pop();
        console.log(e.n);
    }

    var arr:{n:number}[]=[{n:1},{n:4},{n:9}]

    arr[9]={n:3}

    console.log(arr[4].n)
    

    while(e = a.pop()){
        console.log(e.n);
    }

    while(a.length){
        if(a.length){
            var e=a.pop();
            console.log(e.n);
        }
    }