JavaScript emulates C # format string _javascript tips

JS analog C # string formatting operation

/***
* * Function: string format substitution operation
***/
String.prototype.format = function () {
 var args = arguments;
 Return This.replace (/\{(\d+) \}/g,
 function (M, i) {return
  args[i];
 }

JS implements the string processing function format () similar to C #:

Familiar with C # should know that there is a format () such a method, the following to imitate, in JavaScript also implement this feature.

The code example is as follows:

String.prototype.format=function (args) { 
 if (arguments.length>0) { 
 var result=this; 
 if (arguments.length==1&&typeof (args) = = "Object") {for 
  (var key in args) { 
  var reg=new RegExp ("{" +key+ "}", "G"); 
  Result=result.replace (Reg, Args[key]); 
  } 
 else{for 
  (var i=0;i<arguments.length;i++) { 
  if (arguments[i]==undefined) {return 
   ""; 
  } 
  else{ 
   var reg=new RegExp ("({[" +i+ "]})", "G"); 
   result = Result.replace (Reg, arguments[i]); 
 }} return result; 
 } 
 else{return this 
 ; 
 }
var fiststr= "{0} welcome you, hope everybody can get want of {1}";
var secondstr= "{WebName} welcome you, hope everybody can get want of {favoriate}";
var Firstout=fiststr.format ("", "something");
var Secondout=secondstr.format ({webName: "", Favoriate: "Something"});
Console.log (firstout);

The above code is to achieve the desired effect, the following describes its implementation process:

I. Principle of realization:

The principle is relatively simple, here to make a long story short, see code comments. Use regular expressions to find the strings to be replaced, and then replace them with the specified content, where the specified content is either a string literal or an object's property value.

Two. Code comments:

1.string.prototype.format=function (args) {}) Adds an instance method format to a string object through a prototype object, which is used to process strings.

2.if (arguments.length>0), if the number of pass parameters is greater than 0.

3.var Result=this, the reference to this is assigned to the variable result.

4.if (arguments.length==1&&typeof (args) = = "Object") is used to determine whether the passed parameter is an object direct amount.

5.for (Var key in args), traversing the attributes in the object's direct volume.

The 6.var reg=new RegExp ("({+key+"}) "," G ") is used to match the specified string.

7.result=result.replace (Reg,args[key]), replaces the matching string with the property value.

8.else{}, if the pass is not a direct amount of an object.

9.for (Var i=0;i<arguments.length;i++), traversing the passed parameters.

10.if (arguments==undefined), if undefined, returns an empty string.

11.var reg=new RegExp ("({[" +i+]}) "," G "), to match the specified string.

12.result=result.replace (reg,arguments), for replacement.

13.return result, returns the replacement string.

14.return this, if no arguments are passed, the string itself is returned.