1use a regular expression like this  
2
3var strNumber = "0049";  
4console.log(typeof strNumber); //string  
5  
6var number  = strNumber.replace(/^0+/, ''); 

11. Using substring()
2The substring() method returns the part of the string between the specified indexes, or to the end of the string.
3
4let str = 'Hello';
5 
6str = str.substring(1);
7console.log(str);
8 
9/*
10    Output: ello
11*/
12 
13The solution can be easily extended to remove first n characters from the string.
14
15
16let str = 'Hello';
17let n = 3;
18 
19str = str.substring(n);
20console.log(str);
21 
22/*
23    Output: lo
24*/
25 
26___________________________________________________________________________
272. Using slice()
28The slice() method extracts the text from a string and returns a new string.
29
30let str = 'Hello';
31 
32str = str.slice(1);
33console.log(str);
34 
35/*
36    Output: ello
37*/
38 
39This can be easily extended to remove first n characters from the string.
40
41
42let str = 'Hello';
43let n = 3;
44 
45str = str.slice(n);
46console.log(str);
47 
48/*
49    Output: lo
50*/
51 
52__________________________________________________________________________
533. Using substr()
54The substr() method returns a portion of the string, starting at the specified index and extending for a given number of characters or till the end of the string.
55
56
57let str = 'Hello';
58 
59str = str.substr(1);
60console.log(str);
61 
62/*
63    Output: ello
64*/
65 
66Note that substr() might get deprecated in future and should be avoided.