next prev function using JavaScript/php

Question

This is the next function that i learn from other's post and i wonder how to do the prev function.

any idea guys? Different approach are welcome as well.

function next() {
    var pElems = document.querySelectorAll('#Pages>div');
    for (var i = 0; i < pElems.length; i++) {
        if (pElems[i].style.display !== 'none') {
            pElems[i].style.display = 'none';
            if (i === pElems.length - 1) {
                pElems[0].style.display = 'block';
            } else {
                pElems[i + 1].style.display = 'block';
            }
            break;
        }
    }
}

Exactly the same, but reverse the array. Or start at the end of the array and do i-- until it's 0. Or use i == pElems.lenghth + 1 in combination with pElems[i - 1].style.display etc. So may possibilities, just play around with it a bit. — Shilly
– Shilly, Commented Dec 23, 2016 at 13:59

Hyddan · Accepted Answer · 2016-12-23 14:04:18Z

1

Your current function steps one element forward: pElems[i + 1], so to go backwards you could just step one backwards pElems[i - 1] and then you have to handle the case of reaching the first element and jump to the end, something like this should do it:

function prev() {
    var pElems = document.querySelectorAll('#Pages>div');
    for (var i = 0; i < pElems.length; i++) {
        if (pElems[i].style.display !== 'none') {
            pElems[i].style.display = 'none';
            if (i === 0) {
                pElems[pElems.length].style.display = 'block';
            } else {
                pElems[i - 1].style.display = 'block';
            }
            break;
        }
    }
}

answered Dec 23, 2016 at 14:04

Hyddan

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