order of execution order in which statements are processed execution contexts one global execution context and each function creates a new execution context the stack JS terp processes on line at a time, stacks new function on top of current task execution context & hoisting when script enters new execution context prepare new scope created variables, functions, arguments created execute assign values to variables reference functions and run code execute statements lexical scope linked to object they were defined within exception JS statement error causes, terp stops and looks for exception-handling code error object shows information about error dealing with errors debug script handle errors gracefully(error handling code) broswer dev tools JS console console object log data to console console.log console.info console.warn console.error console.group console.tab console.assert breakpoints pause execution of script on any line stepping over breakpoint passes over functions, can step into functions conditional breakpoints specify condition to trigger debugger keyword creates breakpoint handling exceptions try specify the code that you think might throw an exception in the try block catch if try code blocks throws exception catch steps with an alternative code set finally will run whether try block succeeds or fails throwing errors create your own error before interpreter creates them