How to execute another function inside a function in JS

How to execute function b inside function a in 1.js

function A (parameter c) {

b ();

}

function B (parameter c) {

}

PS: In the case of the need to pass a parameter, the parameter C inside function A can also be passed into function B.

2. How to execute another function after 20 seconds

function A () {
SetTimeout (b,20000)
}
Function B () {
Alert ("20 seconds later Oh")
}

3. What is a callback function

A callback is a procedure that invokes a function. A callback, a callback, is the meaning of a call back. Function A is done in advance, and then the function B is called back.

Function A has a parameter, which is a function B, and executes function B after function a finishes executing. Then this process is called a callback.

How to execute another function inside a function in JS