Set a conditional breakpoint - Firefox Developer Tools 编辑

A normal breakpoint is just associated with a line: when the program reaches that line, the debugger pauses. A conditional breakpoint also has a condition associated with it, which is represented as an expression. When the program reaches the line, the debugger pauses only if the breakpoint's specified expression evaluates to true.

This makes it possible to debug specific scenarios, such as bugs that only happen on odd entries in a list, or errors that occur the last time through a loop, for example.

To set a conditional breakpoint, activate the context menu in the source pane, on the line where you want the breakpoint, and select "Add Conditional Breakpoint". You'll then see a textbox where you can enter the expression. Press Return to finish.

Conditional breakpoints are shown as orange arrows laid over the line number.

If you context-click on any breakpoint, you'll see a menu item "Edit Breakpoint". You can use this to modify an existing condition or to add a condition to a normal breakpoint.