JavaScript basics (Methods of arrays)

Array of methods (15)

The

object data type; The array member has a corresponding index length: the number of array members, the operation changes the array of methods, the methods of these arrays are built

-in;

//1. Method effect;//2. Parameters of the method//3. Method return value//4. Whether the original array has changed;1.push

1): Add an entry to the end of the array, 2): The parameter is the new item, you can pass multiple; 3): The number of array members of the new array, 4): The original array has changed;

var ary = [12,89,89,36,0, "DSH",true,];ary.push (console.log) (ary );

2.pop

1): Delete the last item of the array 2): Does not need to pass parameter 3): the deleted Item 4): The original array has changed;

Ary.pop (); Delete ary[ary.length-1]console.log (ary[7]); ary.length-;

3:unshift

1): Add an entry to the beginning of the array, 2): Need to pass parameter 3): The number of array members of the new Array 4): The original array has changed;

Ary.unshift (N); console.log (ary);

4.shift

1): Delete the first item of the array 2): no parameter 3): the deleted Item 4): the original array changes;

Ary.shift ();

5.slice

1): Intercept of the array 2): Slice (m,n): Starts from the array index m, intercepts the index n, but does not contain n; [Before Package]slice (m): Starting from index m, intercept to the end; Slice (): Clone of Array slice (0);//Index negative: Let current length+ negative number; 3): Return value is intercepted array 4): The original array does not change;

var ary = [12,89,89,36,0, "DSH",true,];ary.slice ()//  no reference; copy clone Ary.slice (1)//  start at index 1, intercept to the end of the array ary.slice (2,6)//  start at index 2, intercept to index 8, but does not contain 8;  supports negative numbers //  []

6.splice

1): Delete a few items in the array 2): Splice (m,n): Starting from the index, delete n Splice (m): Delete from index m to the end, splice (0): Splice (m,x,n), replace from index m, delete x, replace with N; 3): Return a value, delete those items, and return 4 in an array): The original array has changed;

Ary.splice (0); // starting at index 0, deleting to the end of the array // starting at index 1, delete 4 items ary.splice (1,3,5,19)//  replace ary.splice (1,0,5)//  Add a number 5 to the front of index 1; console.log (ary);

7.sort

1): Array sort 2): parameter

• 1.sort (): Only array members are arrays of the same number of digits
• 2.sort (A, A, b) {return a-B}) sorted from small to large
• 3.sort (function (A, b) {return b-a}) from 3 to 4): Array after sort: The original array has changed;

Ary.sort (): array with the same number of array member digits; var ary = [12,8,99,67,85,1,35,66, "" "]; var ary = [1,8,5,3,2]; var ary = [123,678,987,567,345,234];ary.sort (function  (A, b) {return A- b;}); var newary = Ary.sort (function  (A, b) {return B-A;}); Console.log (newary);

8.reverse

1): Reverse the array 2): Do not need to pass the parameter 3): array member order upside down after the array 4): the original changes;

Console.log (Ary.reverse ()); Console.log (ary);

9.concat:

1): Array of stitching 2):

• 1. Do not pass parameters: cloning of arrays
• 2. Pass parameters, (arrays, each item), stitch the incoming arguments into a new array, 3): New array after stitching 4): The original array does not change;

var ary = [12,8,99,67,66,66,85,1,35,66, "" ","]; var ary1 =[1,2,3]console.log (Ary.concat ([100,200,null])); var a = ary.concat (); Console.log (Ary.concat ());

10.join

1): Concatenate the array members into a string according to a specific character; 2):

• 1. Do not pass parameters, will be separated by commas by default
• 2. Pass parameters, (specific characters) 3): string after stitching 4): The original array does not change;

Console.log (Ary.join ("+")); // "12+8+99+67+85+1+35+66+78"Console.log (Ary.join ("")); // "1289967851356678"Console.log (Ary.join ()); // "12,8,99,67,85,1,35,66,78"

11.indexOf

1): detects the index position of the array member in the array for the first time, determines whether the current item exists in the array, or returns -1;2 if it does not exist: Requires parameter 3): Returns the first occurrence of the index in the array; 4): The original array does not change;

Console.log (Ary.indexof),Console.log (Ary.indexof (666));Console.log (Ary.indexof (888));

12.lastIndexOf

1): detects the last index position of the array member in the array, determines whether the current item exists in the array, or returns -1;2 if it does not exist: Requires parameter 3): Returns the last occurrence of the index in the array; 4): The original array does not change;

Console.log (Ary.lastindexof (66));

Map

1): Traversing array and Mapping 2): Requires parameter 3): Array after mapping 4): The original array does not change;

var ary = [12,8,99,67,66,66,85,1, "" ","]; var NULL ; var mn = Ary.map (function  (item,index) {Console.log (item); // iterating over an array; The first parameter is the array member Console.log (index); // an index that represents an array member return "<li></li>>"; // sum Total + = number(item); Console.log (total); Console.log (MN);

14.forEach

1): traversal array; no return value; 2): Requires parameter 3): The return value is UNDEFINED4): The original array does not change;

var bhh = Ary.foreach (function  (item,index) {Console.log (item); return ;}) Console.log (BHH); // undefinedconsole.log (ary);

15.toString

1): Turn to String 2): No parameter 3 is required: Returns a string that goes after the brackets 4): The original array is unchanged;

var ary = [1,23,8,9,90]console.log (ary.tostring ()); // "1,23,8,9,90"console.log ([12].tostring ()); // "console.log" ([].tostring ()); // "console.log (ary);

JavaScript basics (Methods of arrays)