var oZmkt = document.getElementById('oZmkt')
var input = document.createElement("input");
input.style = "width: 400px;height: 50px;margin-top:100px;";
input.type = 'text'
input.value = '请输入你的手机号'
oZmkt.appendChild(input);
document.querySelector
<form id="oZmkt"></form>