Javascript：如何在单击按钮时显示下一个数组值

Question

I am trying to write a code in javascript/jquery and html which I thought would be fairly simple, but turns out to be quite challenging (to me). I have a program which computes the first x numbers of the fibonacci sequence, and stores it in an array. What I am trying to do is make two buttons that will display the next or previous number in the sequence. This is what I have so far.

Javascript:

var all = new Array();
fib = function (numMax) {
    for (i = 0, j = 1, k = 0; k < numMax; i = j, j = x, k++) {
        x = i + j;
        //window.document.write(x + " ");
        all[k] = x;
    }
};

fib(1000);

fibon = function () {
    getElementById("mynum").innerHTML = "all[+1]";
};

HTML:

<input type="text" id="mynum">
<button onclick="fibon();">Next</button>

Answer 1

You need a variable that contains the current index, and then increment it each time you click.

fibindex = 0;

function fibon() {
    if (fibindex >= all.count) {
        document.getElementById("mynum").value = "We've run out of Fibonacci numbers";
    } else {
        document.getElementById("mynum").value = all[fibindex];
        fibindex++;
    }
}

Also, notice that you should not put quotes around a use of a variable. Add you use .value to fill in an input, not .innerHTML .

DEMO