Preliminary JavaScript Learning

After reading the video tutorial "21 days learning JavaScript", I feel that I am familiar with the syntax, similar to C ++, similar to C #, and similar to Java! Sorry, these languages have similar syntaxes, such as data types and object methods (or functions). Since I am a cainiao, I cannot tell you exactly what it is ).

In JavaScript, data types are classified into integer and floating-point types. Here, the floating-point type does not have the same single-precision or double-precision expression. The declaration of all variables only needs to use VaR (which is easy, do not record int long float double ......) What type of value you pay for it, and what type it is. Also, do not distinguish between characters and strings. In the past, sometimes, when using C #, it seems that "… Cannot be used as a string ". It's easy to remember, haha ............

The string type is similar to the string type in other languages. You can perform operations on the string, such as string truncation substring. The following is an example of a javascript string operation:

 

Javascript string operations

  1   <  Title  >  Example 2 -  10  <  /  Title>  
  2      <  Script Language  =  "  Javascript  "  >  
  3     <! --  
  4     //  Poetry content  
  5        VaR  Comment  =     "  Quiet night Li Bai bed in front of the bright moonlight, suspected to be on the ground frost. Look up at the moon and look down at your hometown.  " ;
  6     VaR  Partial  =  Comment. substring (  0  ,  3  );  //  Retrieve title  
  7      Partial =  Partial. Bold ();  //  Bold title  
  8     Document. Write (  "  <P align = \  "  Center \  "  >  "  );  // Output the HTML Tag "<p>" and set center alignment.  
  9     Document. Write (partial );  //  Output title  
  10     Partial  =  Comment. Slice (  3  ,  5 );  //  Extract author  
  11     Document. Write (  "  <Br/>  "  );  //  Output line feed label <br/>  
  12    Document. Write (partial );  //  Output author  
  13     Partial  =  Comment. Slice (  5  ,  17  );  //  Extract the first poem  
  14    Partial  =  Partial. fontcolor (  "  Gray  "  );  //  Set the color to Gray)  
  15     Document. Write (  "  <Br/>  " );  //  Output line feed label  
  16     Document. Write (partial );  //  Output verse  
  17     Partial  =  Comment. Slice (  17  , 29  );  //  Extract the second poem  
  18     Partial  =  Partial. fontcolor (  "  Gray  "  );  //  Set the color to Gray)  
 19     Document. Write (  "  <Br/>  "  );  //  Output line feed label  
  20     Document. Write (partial );  //  Output verse  
  21    Document. Write (  "  </P>  "  );  //  Output the end tag of the HTML Tag "<p>"  
  22     -->  
  23     <  / SCRIPT> 

 

Composite data types in Javascript

Arrays and functions are also available in JavaScript. The definition of arrays is similar to that of C # And C ++.

The following is an example of an array:

Looking at the sudden appearance, there is an interesting operator in Javascript, "=", which is used to determine whether data is equal, the data must be equal not only in values but also in data types. Oh, this is a bit dizzy.

 

  1   <  Script  >  
  2     <! --  
 3     VaR  X  =  10  ;
  4     VaR  Y  =  Null  ;
  5     If  (X =  Null  )
  6   {
  7   Document. Write (  "  The value of X is null. <br/>  "  );  //  Output prompt  
  8     }
 9     If  (  Null  =  Y)
  10   {
  11   Document. Write (  "  The value of Y is null. <br/>  "  )  //  Output prompt 
  12     }
  13     -->  
  14     <  /  SCRIPT> 

 

Conversion of values in Javascript

There are also conversions of numeric types in Javascript, including display conversions and implicit conversions, which are basically similar to those of C ++. As this is a note, I will not write it.
And almost all webProgramming LanguageSimilarly, "=" and "=" are different. One is to determine whether the value is equal, and the other is to determine whether the value and type are completely equal. I want to take notes separately later. It's already quite long. For me, I have never written such a long thing ...... There is no habit of writing notes separately.

It's sent here today ...... Continue later.

Good good study, day up!