javascript - Questions about try, catch, throw?

Question

try{
    var num = pompt("请输入5~10");
}
catch(err){
    console.log(err);
    console.log(err + "这里我随便加上一段字符串");
}

In the above code, console.log(err); is output on the console like this: ReferenceError: pompt is not defined at index.html:37, there is a prompt line Number.
Butconsole.log(err "I will add a random string here");The output in the console is like this: ReferenceError: pompt is not definedHere I will add a random string String , if a string is added, no error line number will be prompted. What is the reason for this?

Answer 1

The first sentence prints an object.

The second sentence prints a string. That is, err.toString() + "I just add a string here"

try{
    var num = pompt("请输入5~10");
}
catch(err){
    console.log(err);
    console.log(err.toString());
}

Non-professional answer, for reference only-. -

Answer 2

You will know after logging err.toString()

Because err+str, err first calls toString to convert it into a string.

Answer 3

try{
    var num = pompt("请输入5~10");
}
catch(err){
    console.log(err);
    console.log(err , "这里我随便加上一段字符串");
} 

It can be like this

Answer 4

err is data in the form of an object, and is automatically converted into a string when connected with a plus sign.