How to debug code when js encounters code problems-JS Tutorial-php.cn

How to debug code when js encounters code problems

angryTom

Release： 2020-02-05 17:54:19

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This article introduces the debugging method if you encounter problems when writing JavaScript code. I hope it will be helpful to all students learning JavaScript!

How to debug code when js encounters code problems

How to debug code when js encounters code problems

Single-step tracking debugging debugger;

The console watch function checks the current value of the variable

Enters the function operation

As it continues Click to continue looping, and the value of the specified variable is also changing

Add a breakpoint

Jump in Jump out of the function

throw new Error() actively throws an exception

The following code will no longer run

The code will jump Go to the try statement closest to this sentence

Use

try{
}catch(e){
}

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Receive exception

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <script>
        try{
            var foo={};
            console.log(foo.pro);
        }catch(e){
            console.log(e);//undefined
        }finally{
            console.log(&#39;异常导致程序中止啦~&#39;);//异常导致程序中止啦~
        }
    </script>
</body>
</html>

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<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <script>
        function multi(num1, num2){
            if(typeof num1 != "number" || typeof num2 != "number"){
                throw new Error(&#39;必须输入数字!!!&#39;);
            }
            console.log(num1*num2);
        }

        try{
            //multi("a", "b");//Error: 必须输入数字!!!
            multi(1, 2);//2

        }catch(e){
            console.log(e);
        }finally{
            console.log(&#39;不管有没有异常我都要执行哈~&#39;);
        }
    </script>
</body>
</html>

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