How to print the properties and methods of javascript String object.

Following snippet does not print anything.

for (x in String) {
   document.write(x);   
}

How to print the properties and methods of javascript String object.

Following snippet does not print anything.

for (x in String) {
   document.write(x);   
}

• javascript

Share Improve this question Follow asked Apr 10, 2013 at 7:36 minilminil 7,1551616 gold badges5151 silver badges5757 bronze badges 1

• possible duplicate of Is it possible to get the non-enumerable inherited property names of an object? – Joseph Commented Apr 10, 2013 at 7:46

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 9

The properties of String are all non-enumerable, which is why your loop does not show them. You can see the own properties in an ES5 environment with the Object.getOwnPropertyNames function:

Object.getOwnPropertyNames(String);
// ["length", "name", "arguments", "caller", "prototype", "fromCharCode"]

You can verify that they are non-enumerable with the Object.getOwnPropertyDescriptor function:

Object.getOwnPropertyDescriptor(String, "fromCharCode");
// Object {value: function, writable: true, enumerable: false, configurable: true}

If you want to see String instance methods you will need to look at String.prototype. Note that these properties are also non-enumerable:

Object.getOwnPropertyNames(String.prototype);
// ["length", "constructor", "valueOf", "toString", "charAt"...

First It must be declared as Object,(may be using 'new' keyword)

s1 = "2 + 2";               
s2 = new String("2 + 2");   
console.log(eval(s1));      
console.log(eval(s2));      

OR

console.log(eval(s2.valueOf()));

try using the console in developer tools in Chrome or Firebug in Firefox.

and try this

    for (x in new String()) {
       console.log(x);   
    }

This should do the job :

 var StringProp=Object.getOwnPropertyNames(String);

 document.write(StringProp); 

 -->>  ["length", "name", "arguments", "caller", "prototype", "fromCharCode"]

But you might be more interested by :

 var StringProtProp=Object.getOwnPropertyNames(String.prototype);

 document.write(StringProtProp); 

-->> ["length", "constructor", "valueOf", "toString", "charAt", "charCodeAt", "concat", 
"indexOf", "lastIndexOf", "localeCompare", "match", "replace", "search", "slice", "split", 
"substring", "substr", "toLowerCase", "toLocaleLowerCase", "toUpperCase", "toLocaleUpperCase",
 "trim", "trimLeft", "trimRight", "link", "anchor", "fontcolor", "fontsize", "big", "blink", 
"bold", "fixed", "italics", "small", "strike", "sub", "sup"]