Js object-oriented learning note 2 (debug debugging method)

Js object-oriented learning note 2 (debug debugging method)

1. js debugging

 

Obviously, js debugging can only be printed through alert

alert(id);

For complex data types, we can convert them to json format before the pop-up

alert(JSON.stringify(data));

2. DOM information debugging
The information we need to obtain can be printed to the dom element as required.

Document. write (data); // overwrites the entire document

3. Program-side debugging
Print the required information directly on the program end and exit.

var_dump()print_r()

4. Handle other js error messages

/* =============================Most browsers support a small portion of =========== */window. onerror = handleErrfunction handleErr (msg, url, l) {txt = "There was an error on this page. \ n "txt + =" Error: "+ msg +" \ n "txt + =" URL: "+ url +" \ n "txt + =" Line: "+ l +" \ n "txt + =" Click OK to continue. \ n "alert (txt) return true ;}

5. try catch debugging

/* = === */Try {adddlert ("Welcome guest! ");} Catch (err) {txt =" An error occurred on this page. \ N "; txt + =" error Description: "+ err. message +" \ n "; txt + =" click "OK" to continue. \ N "; alert (txt );}

6. Of course, you can use console. log if an error occurs in the PC browser.

console.log(data);