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CSS

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JavaScript

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HTML 

              
                main.content
  .content__select
    label(for="select01") 質問1
    select#select01.js-selectSample.js-check
      option(value='') 選択してください
      option(value='1-1') 選択肢1-1
      option(value='1-2') 選択肢1-2
    p.js-error__required.is-hide 質問1を選択してください
  .content__select
    label(for="select02") 質問2
    select#select02.js-selectSample.js-check
      option(value='') 選択してください
      option(value='2-1') 選択肢2-1
      option(value='2-2') 選択肢2-2
      option(value='2-3') 選択肢2-3
    p.js-error__required.is-hide 質問2を選択してください
  div
    a#link.js-submit.is-disabled(href='https://example.com/') 結果を見る
  p.content__hint ↑↑リンク：
    span#linkText https://example.com/
!

CSS 

              
                .js-error__required {
  line-height: 1;
  color: red;
  font-size: 10px;
  margin-top: 5px;
}
.is-hide {
  display: none;
}
.is-disabled {
  opacity: 0.7;
  pointer-events: none;
}

// only for layout
.content {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 20px;
}

.content__select {
  margin: 15px 0;
}

.content__hint {
  font-size: 14px;
  margin-top: 15px;
}
!

JS 

              
                $(function() {
  const formSelect = $('.js-selectSample');
  const link = $('#link');
  const linkText = $('#linkText'); // codepen用
  formSelect.on('change', function() {
    // formSelectを配列で取得し、&で繋ぐ
    const valueArray = formSelect.map(function() {
      return `${$(this).val()}`;
    }).get().join('&');
    // 選択肢によって新しいurlを発行する
    const hrefTop = "https://example.com/";
    const lower01 = "lower-1";
    const lower02 = "lower-2";
    const lower03 = "lower-3";
    const lower04 = "lower-4";
    const lower05 = "lower-5";
    const lower06 = "lower-6";
    if(valueArray == "1-1&2-1") {
      link.attr({href: hrefTop + lower01});
      linkText.html(hrefTop + lower01); // codepen用
    } else if (valueArray == "1-1&2-2"){
      link.attr({href: hrefTop + lower02});
      linkText.html(hrefTop + lower02); // codepen用
    } else if (valueArray == "1-1&2-3") {
      link.attr({href: hrefTop + lower03});
      linkText.html(hrefTop + lower03); // codepen用
    } else if (valueArray == "1-2&2-1") {
      link.attr({href: hrefTop + lower04});
      linkText.html(hrefTop + lower04); // codepen用
    } else if (valueArray == "1-2&2-2") {
      link.attr({href: hrefTop + lower05});
      linkText.html(hrefTop + lower05); // codepen用
    } else if (valueArray == "1-2&2-3") {
      link.attr({href: hrefTop + lower06});
      linkText.html(hrefTop + lower06); // codepen用
    } else {
      link.attr({href: hrefTop});
      linkText.html(hrefTop); // codepen用
    }
  });
});

// バリデーション
$('.js-check').on('change', function () {
  let value = $(this).val();
  if (value.length === 0) {
    $(this).addClass('js-error');
    $(this).siblings(".js-error__required").removeClass('is-hide');
  } else {
    $(this).removeClass('js-error');
    $(this).siblings(".js-error__required").addClass('is-hide');
  }
  checkAll();
});

function checkAll() {
  let valid = true;
  const checkEls = $('.js-check');

  for (let i = 0; i < checkEls.length; i++) {
    const val = $(checkEls[i]).val();
    valid &= (!!val && val !== '');
  }

  if (valid) {
    $('.js-submit').removeClass('is-disabled');
  } else {
    $('.js-submit').addClass('is-disabled');
  }
}
!
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