javascript pocket reference

element of arr[i] in the hash array is undefined, the description is not duplicated, it is placed in a hash array } //after the loop is over, remove the hash array varback=[]; for(Back[back.length]inchhash); returnBack ; } console.log (F1 ([1,2,2,1,4,5])); Operating results: ["1", "2", "4", "5"]On the efficiency of execution, especially when the data increases, the hash array does not need to go through the array lookup, so the execution e

1. Array creation and initializationvar obj=new Array ();var arr=[];Can be extended to a certain length, the literal defines the array2. Stack by value Pass reference typeAn array is a reference type, not a value pass,Stack: Automatic allocation and release of the barrel, such as function parameters, local variables advanced after the first-level cacheHeap: Usually released by the programmer, the system rec

On the Internet for JS function parameter transfer way of opinions, here is also on the Internet to choose a better explanation:JS and Java are more similar, understand the Java parameter delivery way to understand JS is not difficult.If the value of a variable is an absolute basic type variable such as:function Add (num) { num+=10; return num; } Num=10; Alert (Add (num)); AELRT (num); // Output 20,10 This result should be meaningless to everyone, the value of the basic type vari

complete example of a reference to a JavaScript file: The code is as follows Copy Code function wpjam_add_scripts () {Wp_register_script (' Plugin_script ', Plugins_url (' Plugin_script.js ', __file__), Array (' jquery '), ' 1.1 ', true);Wp_enqueue_script (' Plugin_script ');}Add_action (' wp_enqueue_scripts ', ' wpjam_add_scripts ');?> Using Wp_enqueue_script to int

space, while B=a, b=3, the key is when a value changed to 5 after the value of B has not changed, this is because the data in the stack can be shared. If the execution of a=3,b=3;a=3 execution of 3 allocated memory, then b=3 will not be allocated in the stack memory storage 3 This value, but let B to point to the existing 3, when a=5, the program to find the stack there is no 5 this value, if there is a to point to 5, if not, then reallocate memory storage 5 , shown in the example above, a=5 re

When variable A is assigned to variable B, the value in the stack is copied to the space allocated for the new variable.How to Understand?Copy codeThe Code is as follows:Var x = y = 1;Y = 2;Alert (x ); What is the value of x?Copy codeThe Code is as follows:Var obj = {};Var sub = {};Sub ['id'] = 3;Obj ['sub'] = sub;Sub ['id'] = 4;Alert (obj ['sub'] ['id']); What is the value of obj ['sub'] ['id? Are they really in line with your expectations?We run two pieces of code separately and found that the

Reference | objects | arrays This article enumerates a variety of JavaScript objects and arrays, along with a brief description of the work done on each of these objects or arrays, and its associated property methods, as well as event handlers, which also indicate that the parent object of the object or array may also need to refer to the online The Super Text Object Hierarchy page (http://www.netscapepress

In Javascript scripts, the parameter reference principle is that the referenced parameter can be modified internally (such as attribute), but the reference corresponding to the parameter cannot be modified.A test example is as follows:Copy codeThe Code is as follows:

Five function typesEach function is an instance of the type. Functions are also objects.Declaring functions:The function Func_name () {} //javascript parser will be the first to read the functions declaration when the program executes, making it available (accessible) var func_name = function () {} before executing any code; The parser executes to the line of code where it is located before it is interpreted.So the function name is a variable that ho

(); Console.log (Arr4.unshift); Returns the length of the new array 2console.log (ARR4); Console.log (Arr4.shift ()); Console.log (ARR4); Console.log (typeof Arr4.shift ()); Console.log (ARR4); var arr5=[0,5,15,10,20, "A", "B", 30];console.log (Arr5.reverse ()); //Changed the original array console.log (Arr5.sort ()); [0,10,15,20,5] converted to a string comparison of the result Console.log (Arr5.sort (A, b) {return a>b}); var colors=[1,2,3];var colors2 =colors.concat (4,[5,6]); Console.log (C

Addspan This. Span=Document.createelement ('span'); varBoxblue= function() {MyBox.style.background= 'Blue'; } //Monitoring EventsBox.addeventlistener ('Click', Boxblue); } //ways to add a spanMyBox.prototype.addSpan= function() { varMybox= This. Box; //the inherited This.span can be brought here. varspan= This. span; Span.innerhtml= 'please teach the great god'; Mybox.appendchild (span); } //new object, and then the argument is an object; NewMybox (

var v1 = []var v2 = {};var v3 = {};function foo (v1, v2, v3) {V1 = [1];v2 = [2];V3 = {A:3}}Foo (v1, v2, v3);Alert (v1); BlankAlert (v2); [Object Object]alert (V3.A); Undefined/* This shows: v1, V2, V3 have not been changed, V1 is still an array of 0 elements, V2, V3 is still a blank object. (description is not a reference pass)* However, arrays, objects, etc. are passed by value, which refers to the value of the variable address.* The values of arrays

This article mainly introduces the JavaScript in the regular expression of the reverse reference, the need for friends can refer to theRecently encountered a requirement, pass in a string, insert a space example every three characters: incoming abcd1234 output ABC D12 34 think about it, prepare to write a function The following code is as follows: function Appendspace (s) {V Ar length = s.length; var result

This is a very simple feature implementation: 　　The execution of this program will show the numbers starting from 0 sequentially, they appear one after another, you can scroll to see it. Now let's take a closer look at the code, and he's using the while (1) condition to create a loop that doesn't stop, and typically, a JavaScript program that constantly uses one and only one thread will cause the browser to look like it freezes, and it will not allow

form 4.2 RegExp Instance methodThe main way to regexp objects is toexec (), the method is specifically designed for capturing groups. EXEC () receives a parameter, which is the string to which the pattern is applied, and then returns an array containing the first occurrence information, or null. The returned array, although an instance of array, contains an additional two properties: Index and input. Where index represents the position of the match in the string, and input represents the s

From: http://www.w3school.com.cn/js/jsref_obj_date.asp A good JS website, The date object is an internal data type of JavaScript. The date object does not have any attribute that can be read and written directly. All accesses to the date and time values are executed through the method. Access detailed information about the date object method from the following table.Date object Method FF: Firefox, N: Netscape, ie: Internet Explorer Method

Conclusion: Numbers and strings are transmitted to function parameters. Changes in function parameters do not affect external variables. For arrays and objects, the value of the variable of the object (array) is passed to the function parameter. This variable is saved to the address of the object (array. When the function changes the content of the object (array) pointed to by this address, it also changes the content of the object (array) pointed to by the function external variable; when a fun

);//green,blue,yellowSplice () Inserts an item into the middle of the arrayDelete: You can delete any number of items by specifying only 2 parameters: the location of the first item to delete and the number of items to delete.Insert: You can insert any number of items into the known location, providing only 3 parameters, starting position, 0 (number of items to delete), and items to insertReplace: You can insert any number of items to the specified location and delete any number of items at the

1. Two ways to create objects:The new operator is followed by the Object constructor;var obj=New Object (); Obj.name= ' big head son '; obj.age= 12;Object literal expression methodvar obj={ name:' big head son ', age :n};2. two ways to Access object Properties :Console.log (obj["name"]); Console.log (obj.age); /* Big head son */Functionally, there is no difference between the two methods of accessing object properties. But the advantage of square brackets is that you can access the property

code is as follows:function sum (num1,num2) { return num1+num2;} function Applysum (num1,num2) { return sum.apply (this,arguments);/* parameter The first is the scope in which the function is run, the second argument is the array equivalent to return Sum.apply (this,[num1,num2]); */}function callsum (num1,num2) { return Sum.call (THIS,NUM1,NUM2);/* The first parameter is the scope in which the function is run, followed by a parameter */}console.log (Applysum (10,10));//20console.log (C