null undefined

= = and = = Definition==and === Although they are all relational expression operators, they are defined differently: ==: Called the equality Operator (equality Operator), which is used to detect the equality of two operations, where the

As long as the variable that is intended to hold the object does not actually hold the object, you should let the variable hold a null value. Conversion rules for number () functions If NULL, returns 0; If it is undefined, return

= = equals, that is, the value is equal after the conversion.Console.log ("1.23" ==1.23); // trueConsole.log (0==false); // trueconsole.log (null==undefined); // trueconsole.log (new object () = =New object ()); // falseConsole.log ([1,2]==[1,2]); //

xTable of Contents [1] identity [2] equal [3] greater than [4] less than the preceding wordsThe relational operator is used to test the relationship between two values, and returns TRUE or false depending on whether the relationship exists, and the

Recently, because of the source code in the reading Underscore.js, plus the IFE before the completion of the JavaScript part of the Task2, which a large number of abbreviated sentence wording, especially like?: This trinocular operator is combined

${content}

In the JavaScript this keyword detailed article, we talked about the following to make a simple review:The meaning of a 1.this object is to point to properties and methods in the current object.The variability of the 2.this point. This points to the

1. Character Set Unicode characters. Each character in Javascript (Js) programs is expressed in two bytes. A 16-bit Unicode code can represent every written language commonly used on the earth. 2. Data Type Number) All numbers are represented in

1.Convert using a Boolean object Copy codeThe Code is as follows: var num123 = 123, str = 'abc', o = {name: 'test'}, num0 = 0; num123 = Boolean (num123 ); // true num0 = Boolean (num0); // false str = Boolean (str); // true o = Boolean (o); // true

There are 6 values of "false" in JavaScript, and these six values are: False Null Undefined 0 "(empty string) NaN In this case, false itself is a Boolean type, and the other 5 are not.In addition to these 6, the

The following data types are defined in javascript: Strings (String) Numbers (number) Boolean (Boolean) Arrays (Array) Objects (object) Null (NULL) Undefined (Undefined) 1. StringA string is any text enclosed in

1, JS basic data type has number, String, number, Null, Undefined, Boolean, there is a complex data type Object,function and array is a derived type of object.2, typeof used to determine the data type of a given variable,"Undefined"-this value is

Javascript NoteChapter one 1.1 values       JS has six basic value types: number,string,boolean,object,function,undifined1.2 The number computer uses a sequence to store data in memory, JS uses a fixed-length bit sequence of 64 to hold numeric

/*1. Get the logical pixel var pagewidth = Window.innerwidth;var PageHeight = Window.innerheight;console.log ("pagewidth:" + pageWidth); Console.log ("PageHeight:" + pageheight), if (typeof pagewidth! = "Number") {if (Document.compamode = = =

Boolean null undefined number String Symbol (ECMAScript 2015)The type can be detected by TypeOf.var x = 1; Console.log (typeof x);//number var a = undefined; Console.log (typeof a);//undefined var b =

First, what is JavaScript?Before we talk about the basis of JS, let us know what is JS Bar.JS, full name JavaScript. is a literal translation scripting language, a dynamic type, a weak type, a prototype-based language, and a built-in support type.

An abstract problem in the actual sceneWhat does the following this point to? var a = { function() { Console.log (this); }, function() {

JavaScript notesFirst, JavaScript introduction1,javascript is a computer programming language that defines variables like other programming languages, executes loops, and so on.2,javascript code is primarily executed on the browser, providing

Data typein the ES , there are 6 basic data types :number,String,Boolean , Null,Undefined, and ES6 Newly added SymbolUndefined Data TypesThere is only one value for this data type:undefiendwhen a variable is declared, but the variable is not

In js, "= = =" is called the strict operator, "= =" is called the equality operator.The difference is that the equality operator ( == ) compares two values for equality, and the strict equality operator ( === ) compares whether they are "the same