Idioms Beginning with j

• jump down someone's throat

  To yell at or criticize with excessive and unexpected harshness
  What’s wrong with Max? I just asked him how he was doing, and he jumped down my throat for no reason.

• jump on the bandwagon

  To adopt a popular activity or trend.
  Everyone is jumping on the bandwagon and buying electric cars now.

• jump the gun

  To do something too soon, before the right time.
  Max jumped the gun and proposed before they had even discussed marriage.