361

I want to delete the first character of a string, if the first character is a 0. The 0 can be there more than once.

Is there a simple function that checks the first character and deletes it if it is 0?

Right now, I'm trying it with the JS slice() function but it is very awkward.

13 Answers 13

539
var s = "0000test";
while(s.charAt(0) === '0')
{
 s = s.substr(1);
}

This will kill any 0's at the start of the string.

  • 11
    @Stephen: In this case, it wouldn't make a difference because charAt always returns a string, even if the index exceeds the index of the last character, so there's no type coercion performed, and the algorithm ends up being identical. But I do prefer === over == even when it doesn't make a difference. ;) – user113716 Oct 17 '11 at 21:32
  • 1
    @user113716 Wouldn't that exactly be the reason to use === so that javascript doesn't have to check if the types are the same? – Hejner Feb 11 '13 at 13:07
  • 4
    @Hejner: If the types are the same, as they always would be in this case, then === and == perform precisely the same steps (according to the spec, at least), so there is no reason to expect one to perform better than the other. – Tim Down Oct 28 '13 at 9:40
  • 2
    @MiguelCoder. According to the spec, the steps are the same (browser implementations may differ, of course). Read it if you don't believe me. – Tim Down Jul 13 '18 at 9:12
  • 2
    @ReallyNiceCode putting aside the fact that the question was asked over 8 years ago. It was stated "The 0 can be there more than once." and the asker accepted my solution. – Shaded Mar 26 at 13:41
142

Very readable code is to use .substring() with a start set to index of the second character (1) (first character has index 0). Second parameter of the .substring() method is actually optional, so you don't even need to call .length()...

TL;DR : Remove first character from the string:

str = str.substring(1);

...yes it is that simple...

Removing some particular character(s):

As @Shaded suggested, just loop this while first character of your string is the "unwanted" character...

var yourString = "0000test";
var unwantedCharacter = "0";
//there is really no need for === check, since we use String's charAt()
while( yourString.charAt(0) == unwantedCharacter ) yourString = yourString.substr(1);
//yourString now contains "test"

.slice() vs .substring() vs .substr()

Quote from (and more on that in) What is the difference between String.slice and String.substring?

He also points out that if the parameters to slice are negative, they reference the string from the end. Substring and substr doesn´t.

76

Use .charAt() and .slice().

Example: http://jsfiddle.net/kCpNQ/

var myString = "0String";

if( myString.charAt( 0 ) === '0' )
    myString = myString.slice( 1 );

If there could be several 0 characters at the beginning, you can change the if() to a while().

Example: http://jsfiddle.net/kCpNQ/1/

var myString = "0000String";

while( myString.charAt( 0 ) === '0' )
    myString = myString.slice( 1 );
54

The easiest way to strip all leading 0s is:

var s = "00test";
s = s.replace(/^0+/, "");

If just stripping a single leading 0 character, as the question implies, you could use

s = s.replace(/^0/, "");
17

You can do it with substring method:

let a = "My test string";

a = a.substring(1);

console.log(a); // y test string
16

Did you try the substring function?

string = string.indexOf(0) == '0' ? string.substring(1) : string;

Here's a reference - https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/substring

And you can always do this for multiple 0s:

while(string.indexOf(0) == '0')
{
    string = string.substring(1);
}
6
var s = "0test";
if(s.substr(0,1) == "0") {
    s = s.substr(1);
}

For all 0s: http://jsfiddle.net/An4MY/

String.prototype.ltrim0 = function() {
 return this.replace(/^[0]+/,"");
}
var s = "0000test".ltrim0();
  • Yeah, this would work, if only one 0 is in the string. But i need it also if the String looks like var s = "00test0"; then only the first two 0 had to be replaced – Jings Dec 30 '10 at 16:43
  • 1
    you didnt say that – zsalzbank Dec 30 '10 at 16:43
  • Yeah i know, sry for that :) – Jings Dec 30 '10 at 16:44
  • 1
    Why not charAt? Why the brackets? Why a prototype extension? Yuck. – Ry- Aug 7 '13 at 17:24
6
//---- remove first and last char of str    
str = str.substring(1,((keyw.length)-1));

//---- remove only first char    
str = str.substring(1,(keyw.length));

//---- remove only last char    
str = str.substring(0,(keyw.length));
3

Here's one that doesn't assume the input is a string, uses substring, and comes with a couple of unit tests:

var cutOutZero = function(value) {
    if (value.length && value.length > 0 && value[0] === '0') {
        return value.substring(1);
    }

    return value;
};

http://jsfiddle.net/TRU66/1/

3

String.prototype.trimStartWhile = function(predicate) {
    if (typeof predicate !== "function") {
    	return this;
    }
    let len = this.length;
    if (len === 0) {
        return this;
    }
    let s = this, i = 0;
    while (i < len && predicate(s[i])) {
    	i++;
    }
    return s.substr(i)
}

let str = "0000000000ABC",
    r = str.trimStartWhile(c => c === '0');
    
console.log(r);

2

try

s.replace(/^0/,'')

console.log("0string  =>", "0string".replace(/^0/,'') );
console.log("00string =>", "00string".replace(/^0/,'') );
console.log("string00 =>", "string00".replace(/^0/,'') );

0
var test = '0test';
test = test.replace(/0(.*)/, '$1');
  • 2
    This doesn’t perform as expected and is also really inefficient. – Ry- Aug 7 '13 at 17:25
0

From the Javascript implementation of trim() > that removes and leading or ending spaces from strings. Here is an altered implementation of the answer for this question.

var str = "0000one two three0000"; //TEST  
str = str.replace(/^\s+|\s+$/g,'0'); //ANSWER

Original implementation for this on JS

string.trim():
if (!String.prototype.trim) {
 String.prototype.trim = function() {
  return this.replace(/^\s+|\s+$/g,'');
 }
}

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