try{
var b = 7 ;
setTimeout(function(){console.log(b);throw new Error("")},2000)
}catch(e){
console.log(1)
console.log(e.message)
}console print result
7;
Uncaught Error:
at <anonymous>:3:48printing out 7 means that after the try has finished executing the code, it still retains its context without popping the stack. After the timer is executed in the timer module, the bound callback function is put into the task queue, then taken out by the js execution stack, and put into the scope of the try (because of the scope of the js function, internal variables cannot be accessed externally. At this point, the value of b means that the execution scope of the callback function is within try), so why does catch not catch the exception thrown in the try at this time?