Instructions for using JavaScript arrays

The definition of JS array:

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Method 1. var mycars=new Array () mycars[0]= "Saab" mycars[1]= "Volvo" mycars[2]= "BMW" Method 2. Define and initialize together: var mycars=new Array ("Saab", "Volvo", "BMW") Or another way of writing: var mycars=["Saab", "Volvo", "BMW"];

2, access to elements of the array

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var testgetarrvalue=arrayobj[1]; Gets the element value of an array Arrayobj[1]= "This is the new value"; Give a new value to an array element

3, the addition of array elements

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Arrayobj. Push ([Item1 [item2 [...] [Itemn]]]); /Adds one or more new elements to the end of the array and returns the new length of the array Arrayobj.unshift ([Item1 [item2 [...] [Itemn]]]); /Adds one or more new elements to the beginning of the array, the elements in the array are automatically moved back, and the new length of the array is returned Arrayobj.splice (insertpos,0,[item1[, item2[, ...) [, Itemn]]]); /inserts one or more new elements into the array at the specified position, and the element at the insertion point is automatically moved back to "".

4, the deletion of the elements of the array

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Arrayobj.pop (); Removes the last element and returns the element value Arrayobj.shift (); Removes the first element and returns the element value, and the elements in the array are automatically moved forward Arrayobj.splice (Deletepos,deletecount); Deletes the specified number of DeleteCount elements starting at the specified position, deletepos the removed elements

5, the array of interception and merging

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Arrayobj.slice (start, [end]); Returns a portion of an array as an array, noting that the end-corresponding element is not included, and if omitting the end copies all elements after start Arrayobj.concat ([item1[, item2[, ...) [, Itemn]]]); Concatenate multiple arrays (or a string, or a mixture of arrays and strings) into an array, returning a new array of connections

6, the copy of the array

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Arrayobj.slice (0); Returns an array of copies, noting that a new array is not a pointer to the Arrayobj.concat (); Returns an array of copies, noting that a new array is not a pointer to the JavaScript two-dimensional array: JavaScript uses one-dimensional arrays to simulate two-dimensional arrays: Method 1. var arr = new Array ([' A ', ' B ', ' C '],[' d ', ' e ', ' f ']); ARR[0] Returns the first one-dimensional array, arr[0][0] returns the first element ' a ' of the first one-dimensional array, the same below. Method 2. Arr=new Array (); for (i=0;i<100;i++) { Arr[i]=new Array (...); } Method 3. var arr=new Array ( New Array (), New Array (), New Array () );

Data Lookup Maximum Value

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function Array_max () { var i, max = This[0]; for (i = 1; i < this.length; i++) { if (Max < this[i]) max = This[i]; } return Max; } Array.prototype.max = Array_max; var x = new Array (1, 2, 3, 4, 5, 6); var y = X.max ();

Array Length:

The JavaScript array does not need to be set in length, it expands itself, and the array name. Length returns the number of elements

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var arr=[12,23,5,3,25,98,76,54,56,76]; Defines an array that contains 10 digits alert (arr.length); Displays the length of the array 10 arr.length=12; Increase the length of an array alert (arr.length); The length of the display array has changed to 12 Alert (arr[8]); Displays the value of the 9th element, which is 56 arr.length=5; Reduces the length of the array to 5, and the elements indexed equal to or more than 5 are discarded Alert (arr[8]); Show 9th element has changed to "undefined" arr.length=10; Restores the array length to 10 Alert (arr[8]); Although the length is restored to 10, the 9th element cannot be retracted, displaying "undefined"

Common functions:

Common functions for arrays

ToString (): Converts an array to a string
toLocaleString (): Converts an array to a string
Join (): Converts an array into a symbolic concatenated string
Shift (): Moves an element of an array's head out
Unshift (): Inserts an element in the header of an array
Pop (): Deletes an element from the tail of an array
Push (): Adds an element to the tail of the array
Concat (): Adding elements to an array
Slice (): Returns the part of an array
Reverse (): Sort the array in reverse order
Sort (): Sorting operations on array
Splice (): Inserts, deletes, or replaces an array element

JavaScript Array Ordering:

Arrayobj.sort (sortfunction)

Parameters

Arrayobj
Array
Sortfunction
Options available. comparison function. If this argument is omitted, then the elements are sorted in ascending order in ASCII characters.
The comparison function must return one of the following values:

* Negative value if the first argument passed is smaller than the second argument.
* Zero if two parameters are equal.
* Positive value if the first argument is larger than the second argument

Example:

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var testarray=[1,5,2,3,6,4] Testarray.sort (function (a,b) {return a-b;}); alert (Testarray);

Summary of array usage methods

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<script language= "JavaScript" > /* Because JavaScript is an untyped language, elements of an array can have arbitrary data types, and different elements of the same array can have different types, the element settings of an array can contain other arrays, so you can create a complex array. And at this point JavaScript is different from the rigorous object-oriented C++.c#,java as a scripting language. With greater flexibility. */ /* * in javascript1.1 and subsequent versions, the array is created with the constructor array () and operator new. You can create an array in JavaScript in the following three ways. */ var a=new Array (); var b=new Array (5,4,3, "a", "test,string"); var c=new Array (20); a[1.23]= "Test"; document.write ("a[1.23]=" +a[1.23]); Believe that every time you learn JavaScript from a strongly typed programming language, you'll definitely be surprised by this action, Float data is also count the group, in fact not what you think JavaScript will convert it to a string when you are using negative numbers, floating-point numbers, (or Boolean, objects, other values) Using the generated string as the property name of the object, rather than defining a new array element The example above is the fact that a property named: "1.23" was created for a. document.write ("a.length=" +a.length); document.write ("b.length=" +b.length); document.write ("c.length=" +c.length); A[3]= "Test"; document.write ("<br/>a[3]=" +a[3)); document.write ("<br/>a.length=" +a.length); The above tests also make it clear that we use integers as subscripts for arrays to actually add an element to the array. This uses the length of the array to reflect the subtleties of the JavaScript array. The  //can truncate the length of an array by setting an array's Length property.  a.length=3;  if (a[3]==undefined)  {   document.write ("<br/> After A.length=" +a.length+ "a[3]=" +a[ 3]);  }  else  {     document.write ("<br/> After A.length=" +a.length+ "a[3]=") ;  }  //here to test our multidimensional array elements  /*  *javascript does not actually support multidimensional arrays  * But we assign elements of one one-dimensional array to one one-dimensional array, This looks like a multidimensional array, but   is actually a one-dimensional array, which is the same idea we have when we understand an array of C, but their implementation mechanism is different.  */  var g=new Array (3);  g[3]=a;  g[3][2]= "Test"  document.write ("< BR/>g[3][2]= "+g[3][2]);    /Array Join () method   for (var i=0;i<20; i++)   {  c[i]=i;  docum Ent.write ("<br/>c[i]=" +c[i));  } The   document.write ("<br/>c element Join () method is followed by:" +c.join ());  //Array reverse () method   C.reverse ();   document.write ("<br/>c element joins in the reverse () method () The result is: "+c.join (" | ")); Testing of the concat () method var h=new Array (1,2,3); H= H.concat ([4,5]); However, the concat function does not recursively expand an array of elements. H=h.concat (6,7,[9,[10,20]]); document.write ("<br/>h.length=" +h.length+ "<br/>" +h); document.write ("h[8]=" +h[8]); Slice () method document.write ("<br>h.slice (4,5) =" +h.slice (4,5)); document.write ("H.slice (5,9) =" +h.slice (5,9)) Slice () method: The returned array contains the element specified by the first argument and the element that starts at the second parameter specified by the Element but does not contain the element specified by the second argument. Splice () method The splice () method is a common method for inserting or deleting an array element. /* The first parameter of the splice function specifies the position of the element to be inserted or deleted in the array. The second parameter specifies the number of elements to be removed from the array After the second parameter, you can have as many parameters as you want, and they specify the elements that are inserted from the position specified by the first parameter. The first element and subsequent elements, make the corresponding move. */ document.write ("<br/>h.splice (8,1) after H is::" +h.splice (8,1)); document.write ("<br/>h.splice (8,0, ' A ', ' B ', ' Test ') after H is:" +h.splice (8,0, ' A ', ' B ', ' Test ')); H.splice (7,0, ' A ', ' B ', ' Test '); document.write ("<br/>h.splice" (7,0, ' A ', ' B ', ' Test ') after H is: "+h); Arrays in JavaScript are similar to PHP when used as stacks This is interesting and more useful. The following is a small instance used as a stack /* The push method is to attach one or more new elements to the end of the array, and then return the new length of the array. The pop deletes the last element of the array, sticks to the length of the array, and returns the value he deleted. */ var stack=new Array (); Stack.push (1,2); document.write ("<br>stack element is:" +stack); document.write ("<br/>stack.length=" +stack.length); The result of the document.write ("<br>stack.pop () return is:" +stack.pop ()); document.write ("<br/>stack.length=" +stack.length); The following is a small instance used as a queue /* The Unshift method adds one or more elements to the head of an array element, and then moves the existing element to the largest position in the subscript and has room , it returns the new length of the host family. Method Shift is to delete and return the first element of the array, and then move all subsequent elements forward to fill the space left by the first element. */ var list=[]; List.unshift (6,2); document.write ("<br >list content is:" +list); The document.write ("<br>list shift method is:" +list.shift ()); In addition, the ToString () method that we are familiar with in Java is left It ' s a piece of cake! document.write (C.tostring ()); In fact, the effect of the array's ToString () method and the no-parameter join () is exactly the same Ok,this ' s chapter for Array,that ' s all! </script>