Functions in JS

What is a function

The meaning of function ： The basic unit of a program , Is a block of code statements to complete a specific task

The function classification ： System function （ Such as parseInt()）、 Custom function （ Such as luck()）

Features of functions

Realize certain functions

You can return a result

There can be parameters

Call the function as soon as you enter

Summary

Functions are the basic unit of a program , Blocks of code statements that complete specific tasks

adopt function Defined function

Function calls are generally used with element events

 

Double loop and jump

What is a double cycle

A circulatory body contains another complete circulatory structure , such as ：

// The outer loop

while( The loop condition 1){

// Inner circulation

     // Cyclic operation 1

     while( The loop condition 2){

          // Cyclic operation 2

     }

}

for( The loop condition 1){

     // Cyclic operation 1

     for( The loop condition 2){

          // Cyclic operation 2

     }

}

while( The loop condition 1){

      // Cyclic operation 1

      for( The loop condition 2){

            // Cyclic operation 2

    }

}

Use of multiple cycles

Be careful

Loops can be nested with each other

Generally no more than three floors

The outer loop variable changes once , The inner loop variable needs to be changed again

99 multiplication table practice :

break sentence

break Statement to terminate a loop , Make the program jump to the next statement outside the loop block

In a loop at break The following statement will no longer execute

break Statements can not only be used in for In circulation , It can also be used in other loops

break Execute the process

while(…) {

// Jump out of current loop , The following code does not execute

     break;

}

break Usually used with conditional statements in loops

Summary

break Used to terminate the loop

stay break The following statement is no longer executed

continue sentence

continue Used to cycle

continue Statements can only be used in loop structures

continue Exit this cycle , Continue the following cycle

continue Execute the process

while(…) {

// The following statement is not executed , Skip this cycle , Enter next cycle

     continue;

}

Usually used with conditional statements ,

Accelerate the cycle

Summary

continue End this cycle , Into the next loop

break And continue The difference between

Understand from the process

Debugging method ：

1. Browser breakpoint debugging 1- Add debugger, The disadvantage is that you will forget to delete , bring bug2- Open the check in the page browser , Click on the source code , Drag the left arrow , You can realize debugging , The advantage is that there is no need to add keywords to the code , The disadvantage is that it is complicated
2. alert() debugging

Use alert() Pop up uncertain data , Determine where the error occurred