I know you can not "Ready" a bonus action. But can you ready an attack action and use the bonus action before the attack action when the action is triggered?
The rule for bonus actions says:
You choose when to take a bonus action during your turn, unless the bonus action's timing is specified, and anything that deprives you of your ability to take actions also prevents you from taking a bonus action.
An example of bonus action's timing specified is like with Monk's Flurry of Blows:
Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action.
So unless the bonus action specifies that you have to take it at a specific time, you can take the bonus action at any point in your turn.
If a member of your party is talking to a guard 40 feet away, could you, for example, do the following?
- Ready an action, the trigger being "If the guard draws his weapon I am going to attack"
- The guard draws his weapon triggering your readied action.
- Use your bonus action to cast 'Misty Step,' which has no timing restrictions, to move 30' towards them, use 10 feet of movement, and attack.