为什么我无法在 if 表达式中调用 Jquery 函数

发布于 2024-10-08 23:29:25 字数 310 浏览 2 评论 0原文

$("#btn1").click(function(){

//CheckMyWeight is called Perfectly here and not in the if loop expression

if ($("#frm1").validationEngine({returnIsValid:true}) && CheckMyWeight() && a === b) {  

}});

为什么我无法在 if 循环表达式中调用“CheckMyWeight()”，但我能够完美调用在“#btn1”函数之后。

原文

$("#btn1").click(function(){

//CheckMyWeight is called Perfectly here and not in the if loop expression

if ($("#frm1").validationEngine({returnIsValid:true}) && CheckMyWeight() && a === b) {  

}});

why i am not able to call the "CheckMyWeight()" in the if loop expression and i am able to call perfectly
after the "#btn1" function.

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筱果果 2024-10-15 23:29:25

如果 && 的左侧返回 false，则不会评估右侧。（因为整个表达式不可能为真）
这称为短路。

如果您想始终调用这两个函数，则应该在条件之外调用它们并将结果分配给变量，并留下注释解释原因：

var isValid = $("#frm1").validationEngine({returnIsValid:true});
var isHeavy = CheckMyWeight();   //Always call both functions
if (isValid && isHeavy && a === b) {  
    ...
}

还有其他解决方法，但它们隐藏了代码的意图。

If the left side of the && returns falsy, the right side won't be evaluated. (since the whole expression cannot possibly be true)
This is called short-circuiting.

If you want to always call both functions, you should call them outside the condition and assign the results to variables, and leave a comment explaining why:

var isValid = $("#frm1").validationEngine({returnIsValid:true});
var isHeavy = CheckMyWeight();   //Always call both functions
if (isValid && isHeavy && a === b) {  
    ...
}

There are other workarounds, but they hide the intention of the code.

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残花月 2024-10-15 23:29:25

下面是一个小程序，用于测试您是否可以在 if 循环表达式中调用“CheckMyWeight()”。它的工作原理是，问题在于 $("#frm1").validationEngine({returnIsValid:true} 尝试通过打破条件。

 <html>
    <head>
    <script type="text/javascript" src="jquery.js"></script>
    <script type="text/javascript">
    $(document).ready(function() {
        alert('body');
        function CheckMyWeight() {
          return true;
        }
        $("#btn1").click(function(){
            var a =1,b=1;
            //CheckMyWeight is called Perfectly here and not in the if loop expression
    //        CheckMyWeight() &&
            if ( CheckMyWeight() && a === b) {
                alert('hi');
        }
        });
    });
    </script>
    </head>
    <body>
    <button id="btn1">Click me</button>
    </body>
    </html>

The below is a small program to test whether u can call the "CheckMyWeight()" in the if loop expression .Its working so the problem is with $("#frm1").validationEngine({returnIsValid:true} try to work by breaking the conditions.

 <html>
    <head>
    <script type="text/javascript" src="jquery.js"></script>
    <script type="text/javascript">
    $(document).ready(function() {
        alert('body');
        function CheckMyWeight() {
          return true;
        }
        $("#btn1").click(function(){
            var a =1,b=1;
            //CheckMyWeight is called Perfectly here and not in the if loop expression
    //        CheckMyWeight() &&
            if ( CheckMyWeight() && a === b) {
                alert('hi');
        }
        });
    });
    </script>
    </head>
    <body>
    <button id="btn1">Click me</button>
    </body>
    </html>

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