JavaScript knowledge Rollup------methods for obtaining constructor names and string processing methods

First, the constructor name gets

Each object has aConstructorproperty of each object.ConstructorProperty describes its constructor.

function Fn () {} var New  The constructor property of the //  True  object describes its constructor

The Obj object used in the following code is the one created here

1. Usestring InterceptionGet constructor Name

//using string interception to getvarstr ="'+Obj.constructor;varSTR1 = Str.replace ('function','|');//replace function characters with | To facilitate interceptionvarStartIndex = Str1.indexof ('|');//Find string intercept start indexvarEndIndex = Str1.indexof ('(');//Find string intercept end indexif(StartIndex! =-1&& EndIndex! =-1 ){    varName = Str1.slice (startindex+2, EndIndex); Console.log (name);}

2. UseRegular ExpressionsGet constructor Name

// using regular expressions to get var reg =/function (. +) \ (/; var name1 = reg.exec (str); Console.log (name1);

3. Using objectsName PropertyGet constructor Name

// Get constructorConsole.log (Obj.constructor.name) with the name attribute; // IE8 not supported below

Combined with the above 3 methods, theIE8 browser can only use string interception has been obtained by the regular expression method, and the advanced browser 3 methods are OK, it is necessary to perform the browser performance testing to make compatible

//compatible with all browsers get the constructor namefunctionGetfnname (FN) {/*if (typeof fn!== ' function ') return;            Return fn.name?    Fn.name:/function (. +) \ (/.exec (fn + ") [1]; */      /*if (typeof fn!== ' function ') return;            return Fn.name | |    /function (. +) \ (/.exec (fn + ") [1]; */            return typeoffn!== ' function '?Undefined:fn.name|| /function (. +) \ (/.exec (fn + ") [1];}functionPersonwu () {}varObj2 =NewPersonwu ();varName =Getfnname (Obj2.constructor); Console.log (name);//Personwu

Second, the String method

var string = ' 123abc456 '; var i = 3//substring (startindex,length) = = substr  usage same console.log ( String.substring (0,i)); // 123  Two parameters indicate starting from the left of the index value 0 to extract the first I character Console.log (string.substring (i));  // 456  If a parameter is passed from the left to the first intercept to the rightmost //Slice (startindex,enindex)Console.log ( String.slice (0,i))  // Pack left not pack right,-1 for right first bit //string.replace (REGEXP/SUBSTR, Replacement)

JavaScript Knowledge Rollup------methods and string handling methods for getting constructor names