js realizes switching around the month

Effect picture:

Click the arrows on the left and right to switch between the previous month or the next month.

jsp content

<!--Time month selection box-->
<table id="querytable" style="border:1px;">
    <tr>
        <td style="width: 20%;">
            <span class="leftspan">
            	<span style="color:#FF0000;">
            		<img src="img/left.jpg" style="height:35px; width:35px;" onclick="reduceMonth()"/>
            	</span>
	    </span>
	</td>
	<td align="center">
		<label id="beginTime" class="kbtn" style="height:100px; width:200px;font-size: 35px;">	
		</label>
	</td>
	<td style="width: 20%;" align="right">
	    <span class="rightspan">
            	<span style="color:#FF0000;">
            		<img src="img/right.jpg" style="height:35px; width:35px;" onclick="addMonth()" />
            	</span>
	    </span>
	</td>
    </tr>
</table>

illustrate:

1), arrow pictures can be downloaded from the Internet

js content

// month addition and subtraction processing
function addMonth() {
	var s = document.getElementById("beginTime").innerHTML;
	var arr = s.split("-");
	var year = parseInt(arr[0]);
	var month = parseInt(arr[1]);
	//determine month
	if (month == 12) {
		year = year + 1;
		month = 1;
	} else {
		month = month + 1;
	}
	document.getElementById("beginTime").innerHTML = year + "-" + month;
	initTable(year, month-1);
}

function reduceMonth() {
	var s = document.getElementById("beginTime").innerHTML;
	var arr = s.split("-");
	var year = parseInt(arr[0]);
	var month = parseInt(arr[1]);
	console.log(year + "/" + month);
	//determine month
	if (month == 1) {
		year = year - 1;
		month = 12;
	} else {
		month = month - 1;
	}
	document.getElementById("beginTime").innerHTML = year + "-" + month;
	initTable(year, month-1);
}

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Reference article

https://blog.csdn.net/sinat_16463137/article/details/61925606