JavaScript array Operations

  This article mainly introduces JavaScript array operations, including creation, element access, element deletion, copy of array, and so on, as well as other examples, the friends you need can refer to the following

1, the creation of the array     code as follows: var arrayobj = new Array ();　Creates an array of var arrayobj = new Array ([size]); Create an array and specify the length, note that is not the upper limit, is the length var arrayobj = new Array ([element0[, element1[, ...　[, ELEMENTN]]]); Create an array and assign a value     to illustrate, although the second method creates an array that specifies the length, in all cases the array is longer, that is, even if the length is specified to be 5, the element can still be stored outside the specified length, note: the length changes.   2, the elements of the array access     code is as follows: Var testgetarrvalue=arrayobj[1]; Gets the element value of the array arrayobj[1]= "This is the new value"; Give the array elements a new value     3, add the elements of the array     code as follows: Arrayobj. Push ([Item1 [item2 [...] [Itemn]]]); /Adds one or more new elements to the end of the array and returns an array of new length 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 array elements   code is as follows: Arrayobj.pop (); Removes the last element and returns the element value Arrayobj.shift (); Removes the first element and returns the element value, which automatically moves the element forward arrayobj.splice (Deletepos,deletecount); Deletes the specified number of DeleteCount elements starting at the specified location, deletepos the removed elements     5, intercepting and merging the array   code as follows: 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 will replicate all elements arrayobj.concat after start ([item1[, item2[, ...). [, Itemn]]]); Concatenate multiple arrays (or a string, or a mixture of arrays and strings) into an array, return the concatenated new array     6, and the copy of the array   code as follows: Arrayobj.slice (0); Returns an array of copies, noting that a new array is not pointing to Arrayobj.concat (); Returns an array of copies, noting that a new array, not pointing to     7, sorting the array elements     code is as follows: Arrayobj.reverse (); Reverse element (top to last, last row to top), return array address arrayobj.sort (); The array element is sorted, the address     8, array elements are returned with the string   code as follows: Arrayobj.join (separator); Returns a string that connects each element value of an array, separated by a separator in the middle.     toLocaleString, toString, valueof: Can be seen as a special use of join, not common   two, the Array object 3 properties   1, Length property   Length property sheet Shows the length of the array, which is the number of elements. Because the index of an array always starts with 0, the upper and lower bounds of an array are: 0 and length-1 respectively. Unlike most other languages, the length property of a JavaScript array is variable, which requires special attention. When the length property is set larger, the state of the entire array does not actually change, only the length property is larger, and when the length property is set to the previous hour, the value of the element whose index is greater than or equal to length in the original array is lost. The following is an example of changing the length property:     Code as follows: Var arr=[12,23,5,3,25,98,76,54,56,76]; Defines an array alert (Arr.length) that contains 10 digits; Displays the length of the array arr.length=12; Increase the length of the array alert (ARR.LENGTH); The length of the display array has changed to alert (Arr[8]); Displays the value of the 9th element, which is arr.length=5; Reduces the length of the array to 5, and the element with index equal to or more than 5 is discarded alert (arr[8]); shows that the 9th element has changed to "undefined" arr.length=10; Restores the array length to alert (arr[8]); Although the length is restored to 10, the 9th element cannot be retracted, showing "undefined"     by the above code we can see clearly the nature of the length property. But the length object can be set not only explicitly, it may also be implicitly modified. You can use a variable that is not declared in JavaScript, and you can use an undefined array element (an element whose index exceeds or equal to length), at which point the value of the length property is set to the value plus 1 for the element index used. For example, the following code:   Code is as follows: Var arr=[12,23,5,3,25,98,76,54,56,76]; alert (arr.length); arr[15]=34; alert (arr.length); The     Code also first defines an array of 10 digits, which can be seen by the alert statement as 10. Then the element with index 15 is assigned to 15, or arr[15]=34, and then the length of the array is output by the alert statement, with 16. In any case, this is a surprising feature for developers who are accustomed to strongly typed programming. In fact, an array created with the new Array () has an initial length of 0, and it is an operation that does not define an element in it, which changes the length of the array.     As you can see from the above introduction, the length property is so magical that it makes it easy to increase or decrease the size of the array. Therefore, a thorough understanding of the length attribute is helpful to the flexible application in the development process.   2, prototype property   Returns a reference to the object type prototype. The prototype property is common to object. The   objectname.prototype objectname parameter is the name of the object.   Description: Provides a set of basic functions for an object's class using the prototype property. Object is given the prototype of the object by "inheritance" of the new instanceThe operation.   for array objects, use the following example to illustrate the purpose of the prototype property.   Adds a method to the array object that returns the maximum element value in the array. To do this, declare a function, add it to the Array.prototype, and use it.   Code as follows: function Array_max ()   {     var i, max = this[0];      for (i = 1; I &l T This.length; i++)      {     if (Max < this[i])      max = this[i];     &NBS P;}      return Max;  }   Array.prototype.max = Array_max;   var x = new Array (1, 2, 3, 4, 5, 6);   var y = X.max ();       After the code executes, Y saves the maximum value in the array x, or says 6.   3, constructor property   represents the function that created the object. The   code is as follows: Object.constructor//object is the name of an object or function.     Description: The constructor property is a member of all objects that have prototype. They include all of the JScript intrinsic objects except the Global and Math objects. The constructor property holds a reference to a function that constructs a particular object instance.   For example:   code is as follows: x = new String ("Hi"); if (X.constructor = = String)//To be processed (condition is true).     or   code as follows: function MyFunc {//Functional body. } y = new MyFunc; if (Y.constructor = = MyFunc)//For processing (conditionTo be true).