本案例完全使用原生javascript實現，使用時只需填充platform_list二維數組即可，platform_list填充規則如下：
[‘一級選項1’,‘二級選項11’,‘二級選項12’,‘二級選項13’,‘二級選項14’,…],
[‘一級選項2’,‘二級選項21’,‘二級選項22’,‘二級選項23’,‘二級選項24’,…],
[‘一級選項3’,‘二級選項31’,‘二級選項32’,‘二級選項33’,‘二級選項34’,…]

以省份和城市為例：

const platform_list = [['云南省','昆明市','曲靖市','昭通市','普洱市','楚雄彝族自治州','大理白族自治州','麗江市'],['陜西省','西安市','咸陽市','安康市','寶雞市','商洛市','漢中市','延安市']];

以下是實現二級聯動選框的代碼：

<select name='platform1' id='platform1-select-box'><option value='default'></option>
</select>
<select name='platform2' id='platform2-select-box'><option value='default'></option>
</select>
<script>const platform_list = [//idx0:一級選框選項  idx1~n:對應的二級選框選項['云南省','昆明市','曲靖市','昭通市','普洱市','楚雄彝族自治州','大理白族自治州','麗江市'],['陜西省','西安市','咸陽市','安康市','寶雞市','商洛市','漢中市','延安市']];//生成一級選框選項var platform1SelectElement = document.getElementById('platform1-select-box');var platform2SelectElement = document.getElementById('platform2-select-box')for(var i = 0; i < platform_list.length; i++){a = document.createElement("option");a.value = platform_list[i][0];a.textContent = platform_list[i][0];platform1SelectElement.appendChild(a);}//監聽一級選框變化platform1SelectElement.addEventListener('change', function() {//一級選框選中，獲取對應的二級選項var platform2_list = [];for(var i = 0; i < platform_list.length; i++){if(platform1SelectElement.value == platform_list[i][0]){platform2_list = platform_list[i].slice(1, platform_list[i].length);console.log(platform2_list);break;}}//刪除二級選框已有選項var elements = document.getElementsByName('platform2-option');while(elements.length > 0){elements[0].remove();}//重新生成選項for(var i = 0; i < platform2_list.length; i++){b = document.createElement("option");b.value = platform2_list[i];b.setAttribute('name', 'platform2-option');b.textContent = platform2_list[i];platform2SelectElement.appendChild(b);}});
</script>