Open Chrome Developer Tools via <code>Control-Shift-I</code>
Open Scripts panel and select "script.js" from scripts drop-down
Set breakpoint on line 19 by clicking the line gutter (you can use the Control-G shortcut to reveal a line in a large file)
Move your mouse over this page
You should stop on the breakpoint
Hover over the source code to inspect local and global variables, function arguments etc.
Delete the breakpoint by clicking the blue tag breakpoint indicator
Click the Continue  button or hit F8 in Developer Tools window to resume


Note: All the breakpoints you have set appear under Breakpoints in the right-hand sidebar. Clicking on the entry jumps to the highlighted line in the source file. Once you have a breakpoint set, right click on the blue tag breakpoint indicator to set a conditional statement for that breakpoint. Type an expression and the breakpoint will only pause only if the condition is true.