javascript - 为什么我的整数加起来像字符串

Question

我正在尝试创建一个程序，在给定特定值时为椭圆创建方程。当我尝试添加两个变量时，整数像字符串一样添加。前任。 -4 + 4 应该等于 0 但最终等于 -44

var vertexY = 0
var vertex2Y = 0
function solveEllipse(){
    vertexY = document.getElementById("ellipseVertexYInput").value
    vertex2Y = document.getElementById("ellipseVertexY2Input").value
    centerY = (vertexY + vertex2Y)
    console.log(centerY)
}

<form method="post" class="forms" id="ellipseVertexDiv">
    Vertex
    <br/>
    Y				
    <input type="text" name="vertexY" class="ellipseVariableInput" id="ellipseVertexYInput">
</form>
<form method="post" class="forms" id="ellipseVertex2Div">
    Vertex 2
    <br/>
    Y				
    <input type="text" name="vertexY2" class="ellipseVariableInput" id="ellipseVertexY2Input">
    <input type="button" name="submitButton" value="Submit" class="forms submitButton" id="ellipseSubmit" onclick="solveEllipse()">
</form>

Answer 1

因为 document.getElementById("ellipseVertexYInput").value 返回一个字符串。

您可以使用 + 将其转换为整数:+vertexY

var vertexY = 0
var vertex2Y = 0
function solveEllipse(){
    vertexY = document.getElementById("ellipseVertexYInput").value;
    vertex2Y = document.getElementById("ellipseVertexY2Input").value;
    centerY = +vertexY + +vertex2Y;
    console.log(centerY);
}

<form method="post" class="forms" id="ellipseVertexDiv">
Vertex
<br />
Y				
<input type="text" name="vertexY" class="ellipseVariableInput" id="ellipseVertexYInput">
</form>
<form method="post" class="forms" id="ellipseVertex2Div">
Vertex 2
<br/>
Y				
<input type="text" name="vertexY2" class="ellipseVariableInput" id="ellipseVertexY2Input">
<input type="button" name="submitButton" value="Submit" class="forms submitButton" id="ellipseSubmit" onclick="solveEllipse()">
</form>