如何在jquery中选中或不选中复选框

Question

<div class="avlabs_qw-question question-cust-51" data-page-number="2" style=""> <div class="question-content"><p>What are the main income sources of your website?<span class="tooltip_suggestion_info" data-tool_tip="Select the main income sources you have">i</span></p>
</div><input type="hidden" name="question_id[]" value="51"><input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="189"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-189" class="answer answer-4  answerof-51" value="189" onclick="AvlabsQW.selected_ans_id(189);"><label for="answer-id-189" id="answer-label-189" class=" answer label-4 "><span>Ads</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="196"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-196" class="answer answer-4  answerof-51" value="196" onclick="AvlabsQW.selected_ans_id(196);"><label for="answer-id-196" id="answer-label-196" class=" answer label-4 "><span>Affiliates</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="197"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-197" class="answer answer-4  answerof-51" value="197" onclick="AvlabsQW.selected_ans_id(197);"><label for="answer-id-197" id="answer-label-197" class=" answer label-4 "><span>E-commerce</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="198"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-198" class="answer answer-4  answerof-51" value="198" onclick="AvlabsQW.selected_ans_id(198);"><label for="answer-id-198" id="answer-label-198" class=" answer label-4 "><span>SAAS</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="214"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-214" class="answer answer-4  answerof-51" value="214" onclick="AvlabsQW.selected_ans_id(214);"><label for="answer-id-214" id="answer-label-214" class=" answer label-4 "><span>Other</span></label></div>
<input type="hidden" id="questionType4" value="checkbox" class="required"></div>](https://www.stackoverflow.com/)

<div class="avlabs_qw-question question-cust-51" data-page-number="2" style=""> <div class="question-content"><p>What are the main income sources of your website?<span class="tooltip_suggestion_info" data-tool_tip="Select the main income sources you have">i</span></p>
</div><input type="hidden" name="question_id[]" value="51"><input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="189"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-189" class="answer answer-4  answerof-51" value="189" onclick="AvlabsQW.selected_ans_id(189);"><label for="answer-id-189" id="answer-label-189" class=" answer label-4 "><span>Ads</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="196"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-196" class="answer answer-4  answerof-51" value="196" onclick="AvlabsQW.selected_ans_id(196);"><label for="answer-id-196" id="answer-label-196" class=" answer label-4 "><span>Affiliates</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="197"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-197" class="answer answer-4  answerof-51" value="197" onclick="AvlabsQW.selected_ans_id(197);"><label for="answer-id-197" id="answer-label-197" class=" answer label-4 "><span>E-commerce</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="198"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-198" class="answer answer-4  answerof-51" value="198" onclick="AvlabsQW.selected_ans_id(198);"><label for="answer-id-198" id="answer-label-198" class=" answer label-4 "><span>SAAS</span></label></div>
<input type="hidden" name="answer_ids[]" class="avlabs_qw-answer-ids" value="214"><div class="input_other"><input type="checkbox" name="answer-51[]" id="answer-id-214" class="answer answer-4  answerof-51" value="214" onclick="AvlabsQW.selected_ans_id(214);"><label for="answer-id-214" id="answer-label-214" class=" answer label-4 "><span>Other</span></label></div>
<input type="hidden" id="questionType4" value="checkbox" class="required"></div>

Answer 1

checkBox = document.getElementById('takenBefore');
// Check if the element is selected/checked
if(checkBox.checked) {
    // Respond to the result
    alert("Checkbox checked!");
}