Recursion of JavaScript functions

Recursive

The essence of recursion is to use the function itself to solve the problem of the idea.

definition of recursion (excerpt):

The programming technique called by the program itself is called recursion (recursion). Recursion as an algorithm is widely used in programming language . A procedure or function has a method of directly or indirectly invoking itself in its definition or description, which usually transforms a large and complex problem layer into a smaller problem similar to the original problem, and the recursive strategy can describe the repeated computations needed in the process of solving the problems by a small number of programs. Greatly reduces the code volume of the program. The ability to recursion is to define an infinite set of objects with limited statements . In general, recursion requires boundary conditions, recursive forward segments, and recursive return segments. Recursion advances when boundary conditions are not met, and returns recursively when the boundary conditions are met.

the conditions that make up a recursive requirement:

1. The sub-problem should be the same as the original problem, and simpler.

2. It is not possible to call itself indefinitely, and there must be an exit, simplifying the process of non-recursive status.

first, use the usual way to solve the problem:

There are a bunch of peaches, monkeys eat half a day to throw one, the sixth day of the remaining 1, ask how many Peaches started

    var t=1;      for (i=0;i<6;i++) {        t= (t+1) * *;    }    Alert (t);

If we use a For loop to solve the problem, we need to define a loop that loops six times, that is, six days, the loop (the number of the previous day = the number plus one multiplied by two), and the result is obtained.

If you use recursion to find the number of the third day:

    // recursive    // number of day = (number of next day + 1)    * * // function Explicit: Give a number of days to return the remainder of    the day function Shuliang (ts) {        if(ts==6) {            return 1;        }         return (Shuliang (ts+1) +1) * *;    }    Alert (Shuliang (3));

Here we first want to clear: the number of the day = (Next day quantity + 1)

Then clear the function: give a number of days to return the remainder of the day

function Ideas:

If the number of days is 6, return 1.

Return: Number of day = (number of next day + 1) * *

the procedure for running a function is:

    //days 3, starting the first calculation    functionShuliang (3){        if(ts==6){            return1; }//days are not equal to 6, skip        return(Shuliang (3+1) +1) * *;//call itself, days =3+1, continue function    }    //Number of Days is 4, second calculation        functionShuliang (4){        if(ts==6){            return1; }//days are not equal to 6, skip        return(Shuliang (4+1) +1) * *;//call itself, days =4+1, continue function    }    //Number of Days is 5, third calculation        functionShuliang (5){        if(ts==6){            return1; }//days are not equal to 6, skip        return(Shuliang (5+1) +1) * *;//call itself, days =5+1, continue function    }    //Number of days is 6, fourth time calculation        functionShuliang (3){        if(ts==6){            return1; }//days equals 6, returns 1    }    //The fourth time calculation returns 1 to the third calculation        functionShuliang (5){        return(+) * *;//number of days equals 1, return (*2=4)    }    //The third calculation returns 4 to the second calculation        functionShuliang (4){        return(4+1) * *;//days equals 4, return (4+1) *2=10    }    //The second calculation returns 10 to the first calculation        functionShuliang (3){        return(10+1) * *;//days equals 10, return (10+1) *2=22    }    //Finally, the number returned on the third day is

When the function executes, ts=3, and then enters the function

First time calculation:

TS is not equal to 6, over

Call function itself, ts=4, continue function

Second calculation:

TS is not equal to 6, over

Call function itself, ts=5, continue function

Third-time calculation:

TS is not equal to 6, over

Call function itself, ts=6, continue function

Fourth time calculation:

TS equals 6, returns 1

The fourth time calculation returns 1 to the third calculation,

The third calculation returns (*2=4) to the second calculation,

The second calculation returns (4+1) *2=10 to the first calculation

First calculated return (10+1) *2=22

The number of the third day is 22.

use recursive thinking to find the number of files under a folder

function function: Give the path to a folder, return to the number of files under the folder

    function Shuliang (folder path) {        var sum=0;         if (is file) {            sum+ +;        } Else {            sum=sum+Shuliang (folder path);        }    }

Open Folder

If you encounter a file, the number +1

If you encounter a folder, execute a function, open a folder, if you encounter a file, number +1, if you encounter a folder, execute the function ...

Recursion of JavaScript functions