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form a word \d Digital \d Non-digital \b The boundary of a word \b is not the boundary of a word \ t Horizontal tab \v Vertical tab \f Page break \ r Carriage return character \ n Line break \CA: \cz controls, such as \CM, match a ctrl+m \x0000: \XFFFF Hexadecimal U

(= = =),Non-congruent (not identical) (!==)As with other operators, the following rules are followed when the relational operators manipulate non-numeric values:1. Two operands are numeric, then numerical comparison;2. Two operands are all strings, then the character encoding corresponding to two strings is compared;3. The two operand has one value, then the other is converted to a numeric value, and then the numerical comparison is performed;4. The two operands have one object, then the valueo

"); // return: http://foo.com/bar/file.htmlvar absUrl = $. mobile. path. makeUrlAbsolute ("// foo.com/bar/file.html", "http://foo.com/a/ B /c/test.htm L "); // return: http://foo.com/a/ B /c/test.html? A = 1 B = 2var absUrl = $. mobile. path. makeUrlAbsolute ("? A = 1 B = 2 "," http://foo.com/a/ B /c/test.html "); // return: http://foo.com/a/ B /c/test.html#barvar absUrl = $. mobile. path. makeUrlAbsolute (" # bar "," http://foo.com/a/ B /c/test.html "); 13. $. mobile. path. isSameDomain ()Co

Today, I read the source code of qunit and found a strange piece of code. Although I can understand what it means, I don't understand the role of the double exclamation mark.Copy codeThe Code is as follows:Function id (name ){Return !! (Typeof document! = "Undefined" document. getElementById )Document. getElementById (name );}Then I checked some information on the Internet, which is equivalent to a ternary operator and returns a boolean value.Copy codeThe Code is as follows:Var ret = !! Documen

') btn.addEventListener('click', function(e) { // str = text.value str = '1\n2\n3\n4\n5' var s1 = reg1.test(str) // 空 var s2 = reg2.test(str) // 2345 console.log(RegExp.rightContext) }) 其实到了这一步，对于 m 的用法还不是特别的清晰，后面，我们遇到了真实的问题，会再次回来解决这个问题的。Second, the term and operator 2.1 exact match If a character is not a special character or operator, it means that the character must appear in the expression, such as four characte

1.typeofTypeOf can only judge the basic types, number, String, Boolean, Undefined, and object,function;typeof0;//Number ;typeof true;//Boolean;typeofUndefined//undefined;typeof"Hello World"//string;typeof function(){};//function;typeof NULL;//Objecttypeof{};//object;typeof[];//ObjectAs we can see from the above example, the TypeOf object and array all return object, so it cannot distinguish between objects and arrays.2.instanceofvar a=instanceof Object //truea intanceof Array // false var b

in JavaScript functions (not involving assignments) are advanced to the top of the function body[note] In addition to the variable promotion, the function is also promoted, to the function section will be described in detailvar scope = ‘global‘;function f(){ console.log(scope);//undefined var scope = ‘local‘; console.log(scope);//‘local‘}//变量声明提升之后，相当于下面代码var scope = ‘global‘;function f(){ var scope; console.log(scope);//undefined scope = ‘local‘; console.log(scope);//‘loca

= ' Global '; function f () { var scope; Console.log (scope);//undefined scope = ' local '; Console.log (scope);//' Local ' } There is no block-level scope in JavaScript, so some programmers deliberately place variable declarations at the top of the function body, a source code that clearly reflects the real variable scope Property variables When you declare a JavaScript global variable, you are actually defining a property of the Global object window When you declare a variable

Determine the double exclamation mark in js. I checked some information on the Internet. He is equivalent to a ternary operator and returns a boolean value. Today, I read the qunit source code and found a strange piece of code. Although I can understand what he meant, but I do not understand the role of the Two exclamation points. The Code is as follows: Function id (name ){Return !! (Typeof document! = "Undefined" document. getElementById )Document. getElementById (name );} Then I checked so

Object| Objects | functions Properties: Object.constructorThis property is defined in the prototype of the class, which can be invoked by an object instance after the object instance is created and points to the constructor of the current class. This allows you to determine which class the object directly belongs to (unlike instanceof, instanceof is not limited to the class that the object directly belongs to, even if the parent class returns True).[Example]trace (Object.prototype.constructor =

5.2.2.2 there is no class in the reference data type JavaScript. We can understand it as an object. Parent class of all objects of an Object Instanceof is used to determine the object type. Var obj = new Object ('A'); alert (obj); // aavar obj = new Boolean (10); alert (obj ); // truevar obj1 = new Boolean ("22"); alert (obj1); // truevar obj2 = new Boolean (true); alert (obj2 ); //

In the case of indeterminate variable types, determine if the JavaScript variable is empty and do not use:if (TMP) {}The problem with this judgment is that, for example, when the value of TMP is number 0 o'clock, false is also returned.So try to use:if (tmp! = null) {}The following is the result of the IF (TMP) {} judgment:if (TMP) if (tmp! = NULL)//false//false when TMP is undefinedvar tmp; False//falsevar tmp = 0; False//truevar tmp = 10; True//

CodeVar b1 = Boolean (""); // false;Var b2 = Boolean ("hi"); // trueVar b3 = Boolean (100); // trueVar b4 = Boolean (null); // falseVar b5 = Boolean (0); // falseVar b6 = Boolean (new Object (); // true[Js] view plaincopyVar b1 = Boolean (""); // false;Var b2 = Boolean ("hi"); // trueVar b3 = Boolean (100); // trueVar

. In some cases, the browser wears some foreign values on the regular JS syntax, which is the "False value object".egdocument.all, is a class array object that contains all the elements on the page, provided by the DOM (not provided by the JS engine) to the JS program.The result of forcing type conversion on the browser with document.all can be used to determine if it is IE (old version), which may be hidden in the future because of the end of IE's support for document.all.True value-values outs

variable promotion, the function is also promoted, to the function section will be described in detailvar scope = ' global '; function F () { console.log (scope); var scope = ' local '; Console.log (scope); ' Local '} after the variable declaration is promoted, it is equivalent to the following code var scope = ' global '; functionvar scope; Console.log (scope); undefined scope = ' local '; Console.log (scope); ' Local '} There is no block-level scope in JavaScript, so s

value of 0, which returns true;5. The operand is any non-0 value (including Infinity), false;6. The operand is null and returns true;7. The operand is NaN and returns true;8. The operand is undefined and returns true;var box =! (5 > 4); Falsevar box =! {}; Falsevar box =! "; Truevar box =! ' Lee '; Falsevar box =! 0; Truevar box =! 8; Falsevar box =!null; Truevar