js 移动端点击复制字符串

function copyStr(val) { //val 是要复制的字符串
      var input = document.createElement("input");
      input.value = val;
      input.readOnly = true
      document.body.appendChild(input);
      input.select();
      input.setSelectionRange(0, input.value.length)
      document.execCommand('Copy');
      document.body.removeChild(input);
      window.scrollTo(0, 0)
      alert('复制成功')
    }