Delete first character of string if it is 0

Question

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.

Answer 1

You can remove the first character of a string using substring:

var s1 = "foobar";
var s2 = s1.substring(1);
alert(s2); // shows "oobar"

To remove all 0's at the start of the string:

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

• user113716: @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. ;)
• Tim Down: @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: @MiguelCoder. According to the spec, the steps are the same (browser implementations may differ, of course). Read it if you don't believe me.
• Shaded: @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.
• Soul Reaver: Although still valid, you should update your reply, by replacing substr with substring. Check MDN: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Answer 2

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.substring(1);
//yourString now contains "test"

.slice() vs .substring() vs (削除) .substr() (削除ここまで)

EDIT: (削除) substr() (削除ここまで) is not standardized and should not be used for new JS codes, you may be inclined to use it because of the naming similarity with other languages, e.g. PHP, but even in PHP you should probably use mb_substr() to be safe in modern world :)

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.

Answer 3

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 );

• User 1058612: Works great. Plus, .substr is deprecated.
• justdvl: const pathnameStandardized = pathname.charAt(0) === '/' ? pathname.slice(1) : pathname

Answer 4

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/, "");

Answer 5

You can do it with substring method:

let a = "My test string";
a = a.substring(1);
console.log(a); // y test string

Answer 6

One simple solution is to use the Javascript slice() method, and pass 1 as a parameter

let str = "khattak01"
let resStr = str.slice(1)
console.log(resStr)

Result : hattak01

Answer 7

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);
}

Answer 8

const string = '0My string';
const result = string.substring(1);
console.log(result);

You can use the substring() javascript function.

Answer 9

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();

• Jings: 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
• Ry-: Why not charAt? Why the brackets? Why a prototype extension? Yuck.

Answer 10

//---- 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));

Answer 11

Another alternative answer

str.replace(/^0+/, '')

Answer 12

try

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

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

Answer 13

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/

Answer 14

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);

Answer 15

Another alternative to get the first character after deleting it:

// Example string
let string = 'Example';
// Getting the first character and updtated string
[character, string] = [string[0], string.substr(1)];
console.log(character);
// 'E'
console.log(string);
// 'xample'

Answer 16

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,'');
 }
}

• fino: we don't consider confusion an implementation problem, however, it is often attributed to a capacity deficiency of keeping up with the variables your environment presents to you. In this case, your neural connections are incapable of handling the necessary understanding of this altered adoption of a native js function implementation as an answer to the original question.

Answer 17

var test = '0test';
test = test.replace(/0(.*)/, '1ドル');

• Ry-: This doesn’t perform as expected and is also really inefficient.