How to set the trigger condition of js method to another method of js calls-CodePudding

 
//the source code 
. 
Function a () {
console.log("111"); 
} 
. 
a(); 
. 
//new code 
The function () {b 
The console. The log (" 222 "); 
}

Beginner js food chicken consult
Demand is probably:
Source code is modified
Want a performed immediately b, then continue to execute

Extension step, if can do it before you is to call, be in namely executed before the b

Probably is the analogy of the jQuery event, see a call as an event, b with this event, each incident triggered

By the way, can be directly modified in the b a runtime code?