JS Object 1

1 String Object

String creation

(1) Create directly

var s= "Hello"; Console.log (s); Console.log (typeof s) >>hellostring

(2) Create with class

var s1=new String ("Hello"); Console.log (S1); Console.log (typeof S1) >>helloobject

Properties and functions for string objects

(1) X.length----get the length of the string

　

2 Array Object

Three ways to create an array

(1) var arrname = [element 0, Element 1,....];  var arr1=[11,222,333];        Console.log (arr1);        Console.log (typeof arr1); (2) var arrname = new Array (element 0, Element 1,....), var arr2=new Array ("Yuan", 12,[10,7]);        Console.log (ARR2);        Console.log (typeof arr2), (3) var arrname = new Array (length), var cnweek=new array (7), Var arr3=new array (3);        arr3[0]=12;        Arr3[1]= "Yuan";        Arr3[2]=true;        Console.log (ARR3);        Console.log (typeof Arr3);

Properties and Methods

(1) Join method

X.join (BYSTR)----stitching array elements into strings

Console.log (Arr1.join ("--"));

(2) Concat method

X.concat (Value,...)

Console.log (ARR1.CONCAT);

(3) Array sort-reverse sort

X.reverse ()

X.sort ()

Console.log (Arr4.reverse ());

(4) Array slicing

X.slice (start, end)

var arr2=[12,32,33,100];        Arr2.unshift (a);        Console.log (ARR2);        Arr2.shift (ARR2);        Console.log (ARR2);

　　

Using annotations

x represents the Array object

Start indicates the starting position index

End is the ending position the next array element index number

The first array element index is 0

Start, end can be negative,-1 represents the last array element

End ellipsis is equivalent to intercepting all array elements from the start position

Console.log (Arr4.slice (0,2));

(5) Deleting a sub-array

X. Splice (Start, DeleteCount, value, ...)

Using annotations

x represents the Array object

The main purpose of splice is to delete and insert the specified position in the array

Start indicates the starting position index

DeleteCount to delete the number of array elements

Value represents an array element that is inserted at the drop location

The value parameter can be omitted

Console.log (Arr4.splice (1,0,222)); Console.log (ARR4);

(6) Push and pop for arrays

Push Pop These two methods simulate a stack operation

X.push (value, ...) Press Stack

X.pop () Bomb stack

Using annotations

x represents the Array object

Value can be any value such as a string, a number, an array, etc.

Push is to add value values to the end of the array x

Pop is the last element of the array x is deleted

var arr1=[12,32,5,33,100];        Arr1.push (in);        Console.log (arr1);        Arr1.pop (arr1);        Console.log (ARR1);

(7) The shift and unshift of the array

X.unshift (Value,...)

X.shift ()

x represents the Array object

Value can be any value such as a string, a number, an array, etc.

Unshift is the start of inserting value values into the array x

Shift is to delete the first element of the array x

　

Summary://Convert to String Console.log (Arr1.tostring ()); Console.log (typeof arr1.tostring ());//js regardless of the key plus no quotes, no, the default string        // values, whether single or double quotes, can be        d={"name": "Cobila", "Age": "Max"};        Console.log (d);        Console.log (typeof D);        D1={name: "Cobila", Age: "*"};        Console.log (d1);        Console.log (typeof D1);        Traversing the key-value pair data type for        (var key in D1) {            console.log (key);        }        In JS, when the array is traversed, the index value is obtained;

　　

JS Object 1