原生态js购物框数量加减

html代码

            <div class="dnbc_box">
                <span class="dnbcb_sub" id="sub">-</span>
                <input type="text" value="1" class="dnbcb_inps" id="inp">
                <span class="dnbcb_add" id="add">+</span>
            </div>

js代码

function getId(ogbId) {
        return document.getElementById(ogbId);
    }

    var sub = getId('sub');
    var add = getId('add');
    var inp = getId('inp');
    var inpValue = parseInt(inp.value);
    sub.onclick = function() {
        if (inp.value > 1) {
            inp.value--;
        }
        if (inp.value == 1) {
            sub.style.color = '#999';
        }
    }

    add.onclick = function() {
        inp.value++;
        sub.style.color = '#333';
    }