Copying arrays using JavaScript

I. Error implementation

 

Many people may directly assign values using equal signs:

 

VaR Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
VaR Array2;
Array2 = Array1;
Array1.length =   0 ;
Alert (array2 ); // Return Blank

This is wrong, because JavaScript divides the original type into reference types (similar to Java and C ). Array is a reference class

Type. Array2 gets a reference, so the modification to array1 will affect array2.

 

Ii. Use slice ()

 

You can use slice () for replication because slice () returns an array.

VaR Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
VaR Array2;
Array2 = Array1.slice ( 0 );
Array1.length =   0 ;
Alert (array2 ); // Returns 1, 2, and 3.

 

3. Use Concat ()

 

Note that Concat () does not return the array that calls the function, but a new array, so you can use this to copy.

VaR Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
VaR Array2;
Array2 = Array1.concat ();
Array1.length =   0 ;
Alert (array2 ); // Returns 1, 2, and 3.

 

Iv. Test

Code
<! Doctype HTML public "-// W3C // dtd html 4.01 // en" "http://www.w3.org/TR/html4/strict.dtd" >  
< Html >  
< Head >  
< Meta HTTP-equiv = "Content-Type" Content = "Text/html; charsets = UTF-8" >  
< Title > Array Test </ Title >  
< Script Type = "Text/JavaScript" >  
VaR Array1;
VaR Array2;

Function Clone1 (){
Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
Array2 = Array1;
Array1.length =   0 ;
Alert (array2 );
}

Function Clone2 (){
Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
Array2 = Array1.slice ( 0 );
Array1.length =   0 ;
Alert (array2 );
}

Function Clone3 (){
Array1 =   New Array ( " 1 " , " 2 " , " 3 " );
Array2 = Array1.concat ();
Array1.length =   0 ;
Alert (array2 );
}

</Script> 

</ Head >  
< Body >  
< Input Type = "Button" Value = "Clone1" Onclick = "Clone1 ()"   /> < BR />  
< Input Type = "Button" Value = "Clone2" Onclick = "Clone2 ()"   /> < BR />  
< Input Type = "Button" Value = "Clone3" Onclick = "Clone3 ()"   /> < BR />  
</ Body >  
</ Html >

Both IE8 and ff3.0 pass the test.