How can I put break points in an HTML page in javascript functions to see values of variables as lines get executed. What is the easiest way of doing so?
thanks
Use the keyword "debugger;" to attempt invoking a hard breakpoint.
As long as your browser has Javascript Debugging enabled, then the debugger; statement will tell it to do it's thang and you'll be in a step-by-step debugger.
The Firebug extension for Firefox is by far the easiest, but Internet Explorer's new built-in "Developer Tools" option is quite nice too. Firebug I must say is easier and more polished, but I often must validate in a pile of different browsers and in some cases only Internet Explorer like when debugging the interaction of client-side Javascript and a custom ActiveX control.
The "debugger;" statement always seems to be the golden key to quickly get in to a debugger across platforms and browsers without jumping through a bunch of burning hoops.
So you might have some block of Javacscript like the following, and the browser would invoke the line-by-line debugger on "debugger;" like it was a breakpoint...
var a = 5;
var b = 6;
debugger;
a = b;
You should get Firebug.
In Google Chrome browser press 'Ctrl+Shift+i' buttons.
In IE browser:
- Download Microsoft Javascript debugger.
- In browser goto "Tools->Internet Options->Advanced" and remove "V" from "Disable script debugger" check-box.
Enjoy.
alert(variable);
This is what I do, it pretty much works exactly like a breakpoint. When you press 'OK' the script continues.
来源：https://stackoverflow.com/questions/3571128/javascript-debugging-in-html-file