How do I chop/slice/trim off last character in string using Javascript?

Asked 2023-09-20 20:29:35 View 771,893

I have a string, 12345.00, and I would like it to return 12345.0.

I have looked at trim, but it looks like it is only trimming whitespace and slice which I don't see how this would work. Any suggestions?

  • Do you care about rounding? 12345.46 = 12345.5 or 12345.4? - anyone
  • Do you know what the suffix is or do you want to split and remove the last word based on your underscores? - anyone

Answers

You can use the substring function:

let str = "12345.00";
str = str.substring(0, str.length - 1);
console.log(str);

This is the accepted answer, but as per the conversations below, the slice syntax is much clearer:

let str = "12345.00";
str = str.slice(0, -1); 
console.log(str);

Answered   2023-09-20 20:29:35

  • @Kheu - the slice notation is much cleaner to me. I was previously using the substring version. Thanks! - anyone
  • forgive me if I'm wrong but don't you need to assign the value of str.substring to str again? Like str = str.substring(0, str.length -1); - anyone
  • The slice & substring methods are all most the same; except the that the slice() accepts a negative index, relative to the end of the string, but not the substring, it throws out-of-bound error - anyone
  • In case anybody is wondering, substring is 11% faster than slice. jsperf.com/js-slice-vs-substring-test - anyone
  • substring is insane micro-optimizations which I don't think you should do. Maximize for readability first. Then optimize low hanging fruit if needed. - anyone

You can use slice! You just have to make sure you know how to use it. Positive #s are relative to the beginning, negative numbers are relative to the end.

js>"12345.00".slice(0,-1)
12345.0

Answered   2023-09-20 20:29:35

  • Compared to the accepted solution, this is way more elegant and can be used even with dynamically created strings - anyone
  • I like this way because it jives with php thinking for substr function, easier to remember and write on the fly. - anyone
  • @SameerAlibhai I agree with you, but couldn't the substring method be used on dynamic strings too? By using the str.length to dynamically get the length? - anyone
  • Should be added that the first index is inclusive and the second exclusive. - anyone
  • This works for removing the last character, but beware if you want to remove a variable number of characters; .slice(0, -0) will return an empty string! - anyone

You can use the substring method of JavaScript string objects:

s = s.substring(0, s.length - 4)

It unconditionally removes the last four characters from string s.

However, if you want to conditionally remove the last four characters, only if they are exactly _bar:

var re = /_bar$/;
s.replace(re, "");

Answered   2023-09-20 20:29:35

  • slice is better here. s.slice(0, -4) - anyone
  • Alternatively: s.slice(0, -"_bar".length) (useful if one doesn't want to hardcode the number of characters) - anyone
  • I like this one because he also gives help for replacing a specified ending. - anyone
  • The second example will only remove the first instance of "_bar" if there are multiple instances in the string - anyone

The easiest method is to use the slice method of the string, which allows negative positions (corresponding to offsets from the end of the string):

const s = "your string";
const withoutLastFourChars = s.slice(0, -4);

If you needed something more general to remove everything after (and including) the last underscore, you could do the following (so long as s is guaranteed to contain at least one underscore):

const s = "your_string";
const withoutLastChunk = s.slice(0, s.lastIndexOf("_"));
console.log(withoutLastChunk);

Answered   2023-09-20 20:29:35

For a number like your example, I would recommend doing this over substring:

console.log(parseFloat('12345.00').toFixed(1));

Do note that this will actually round the number, though, which I would imagine is desired but maybe not:

console.log(parseFloat('12345.46').toFixed(1));

Answered   2023-09-20 20:29:35

  • +1 This is what OP needs, forget the false assumption that there are strings to be trimmed. - anyone
  • It is not a false assumption, OP talks about strings. Yours is a false assumption because OP doesn't talk about rounding numbers. - anyone

Be aware that String.prototype.{ split, slice, substr, substring } operate on UTF-16 encoded strings

None of the previous answers are Unicode-aware. Strings are encoded as UTF-16 in most modern JavaScript engines, but higher Unicode code points require surrogate pairs, so older, pre-existing string methods operate on UTF-16 code units, not Unicode code points. See: Do NOT use .split('').

const string = "ẞ🦊";

console.log(string.slice(0, -1)); // "ẞ\ud83e"
console.log(string.substr(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.substring(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.replace(/.$/, "")); // "ẞ\ud83e"
console.log(string.match(/(.*).$/)[1]); // "ẞ\ud83e"

const utf16Chars = string.split("");

utf16Chars.pop();
console.log(utf16Chars.join("")); // "ẞ\ud83e"

In addition, RegExp methods, as suggested in older answers, don’t match line breaks at the end:

const string = "Hello, world!\n";

console.log(string.replace(/.$/, "").endsWith("\n")); // true
console.log(string.match(/(.*).$/) === null); // true


Use the string iterator to iterate characters

Unicode-aware code utilizes the string’s iterator; see Array.from and ... spread. string[Symbol.iterator] can be used (e.g. instead of string) as well.

Also see How to split Unicode string to characters in JavaScript.

Examples:

const string = "ẞ🦊";

console.log(Array.from(string).slice(0, -1).join("")); // "ẞ"
console.log([
  ...string
].slice(0, -1).join("")); // "ẞ"

Use the s and u flags on a RegExp

The dotAll or s flag makes . match line break characters, the unicode or u flag enables certain Unicode-related features. Note that, when using the u flag, you eliminate unnecessary identity escapes, as these are invalid in a u regex, e.g. \[ is fine, as it would start a character class without the backslash, but \: isn’t, as it’s a : with or without the backslash, so you need to remove the backslash.

Examples:

const unicodeString = "ẞ🦊",
  lineBreakString = "Hello, world!\n";

console.log(lineBreakString.replace(/.$/s, "").endsWith("\n")); // false
console.log(lineBreakString.match(/(.*).$/s) === null); // false
console.log(unicodeString.replace(/.$/su, "")); // ẞ
console.log(unicodeString.match(/(.*).$/su)[1]); // ẞ

// Now `split` can be made Unicode-aware:

const unicodeCharacterArray = unicodeString.split(/(?:)/su),
  lineBreakCharacterArray = lineBreakString.split(/(?:)/su);

unicodeCharacterArray.pop();
lineBreakCharacterArray.pop();
console.log(unicodeCharacterArray.join("")); // "ẞ"
console.log(lineBreakCharacterArray.join("").endsWith("\n")); // false


Note that some graphemes consist of more than one code point, e.g. 🏳️‍🌈 which consists of the sequence 🏳 (U+1F3F3), VS16 (U+FE0F), ZWJ (U+200D), 🌈 (U+1F308). Here, even Array.from will split this into four “characters”. Matching those is made easier with the RegExp set notation and properties of strings proposal.

Answered   2023-09-20 20:29:35

  • thanks for your explanation. indeed it widens the horizon. - anyone

Using JavaScript's slice function:

let string = 'foo_bar';
string = string.slice(0, -4); // Slice off last four characters here
console.log(string);

This could be used to remove '_bar' at end of a string, of any length.

Answered   2023-09-20 20:29:35

A regular expression is what you are looking for:

let str = "foo_bar";
console.log(str.replace(/_bar$/, ""));

Answered   2023-09-20 20:29:35

  • This solves a related problem of conditional removing rather than blindly truncating - anyone

Try this:

const myString = "Hello World!";
console.log(myString.slice(0, -1));

Answered   2023-09-20 20:29:35

Performance

Today 2020.05.13 I perform tests of chosen solutions on Chrome v81.0, Safari v13.1 and Firefox v76.0 on MacOs High Sierra v10.13.6.

Conclusions

  • the slice(0,-1)(D) is fast or fastest solution for short and long strings and it is recommended as fast cross-browser solution
  • solutions based on substring (C) and substr(E) are fast
  • solutions based on regular expressions (A,B) are slow/medium fast
  • solutions B, F and G are slow for long strings
  • solution F is slowest for short strings, G is slowest for long strings

enter image description here

Details

I perform two tests for solutions A, B, C, D, E(ext), F, G(my)

  • for 8-char short string (from OP question) - you can run it HERE
  • for 1M long string - you can run it HERE

Solutions are presented in below snippet

function A(str) {
  return str.replace(/.$/, '');
}

function B(str) {
  return str.match(/(.*).$/)[1];
}

function C(str) {
  return str.substring(0, str.length - 1);
}

function D(str) {
  return str.slice(0, -1); 
}

function E(str) {
  return str.substr(0, str.length - 1);
}

function F(str) {
  let s= str.split("");
  s.pop();
  return s.join("");
}

function G(str) {
  let s='';
  for(let i=0; i<str.length-1; i++) s+=str[i];
  return s;
 }



// ---------
// TEST
// ---------

let log = (f)=>console.log(`${f.name}: ${f("12345.00")}`);

[A,B,C,D,E,F,G].map(f=>log(f));
This snippet only presents soutions

Here are example results for Chrome for short string

enter image description here

Answered   2023-09-20 20:29:35

https://stackoverflow.com/questions/34817546/javascript-how-to-delete-last-two-characters-in-a-string

Just use trim if you don't want spaces

"11.01 °C".slice(0,-2).trim()

Answered   2023-09-20 20:29:35

Use regex:

let aStr = "12345.00";
aStr = aStr.replace(/.$/, '');
console.log(aStr);

Answered   2023-09-20 20:29:35

  • Apart from not being Unicode-aware, this also doesn’t match line breaks. - anyone

How about:

let myString = "12345.00";
console.log(myString.substring(0, myString.length - 1));

Answered   2023-09-20 20:29:35

1. (.*), captures any character multiple times:

console.log("a string".match(/(.*).$/)[1]);

2. ., matches last character, in this case:

console.log("a string".match(/(.*).$/));

3. $, matches the end of the string:

console.log("a string".match(/(.*).{2}$/)[1]);

Answered   2023-09-20 20:29:35

  • I like this because in spite of .splice() you found a way to use a regular expression. - anyone
  • Apart from not being Unicode-aware, this also doesn’t match line breaks. - anyone

Here is an alternative that i don't think i've seen in the other answers, just for fun.

var strArr = "hello i'm a string".split("");
strArr.pop();
document.write(strArr.join(""));

Not as legible or simple as slice or substring but does allow you to play with the string using some nice array methods, so worth knowing.

Answered   2023-09-20 20:29:35

debris = string.split("_") //explode string into array of strings indexed by "_"

debris.pop(); //pop last element off the array (which you didn't want)

result = debris.join("_"); //fuse the remainng items together like the sun

Answered   2023-09-20 20:29:35

If you want to do generic rounding of floats, instead of just trimming the last character:

var float1 = 12345.00,
    float2 = 12345.4567,
    float3 = 12345.982;

var MoreMath = {
    /**
     * Rounds a value to the specified number of decimals
     * @param float value The value to be rounded
     * @param int nrDecimals The number of decimals to round value to
     * @return float value rounded to nrDecimals decimals
     */
    round: function (value, nrDecimals) {
        var x = nrDecimals > 0 ? 10 * parseInt(nrDecimals, 10) : 1;
        return Math.round(value * x) / x;
    }
}

MoreMath.round(float1, 1) => 12345.0
MoreMath.round(float2, 1) => 12345.5
MoreMath.round(float3, 1) => 12346.0

EDIT: Seems like there exists a built in function for this, as Paolo points out. That solution is obviously much cleaner than mine. Use parseFloat followed by toFixed

Answered   2023-09-20 20:29:35

if(str.substring(str.length - 4) == "_bar")
{
    str = str.substring(0, str.length - 4);
}

Answered   2023-09-20 20:29:35

Via slice(indexStart, indexEnd) method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.

console.clear();
let str = "12345.00";
let a = str.slice(0, str.length -1)
console.log(a, "<= a");
console.log(str, "<= str is NOT changed");

Via Regular Expression method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.

console.clear();
let regExp = /.$/g
let b = str.replace(regExp,"")
console.log(b, "<= b");
console.log(str, "<= str is NOT changed");

Via array.splice() method -> this only works on arrays, and it CHANGES, the existing array (so careful with this one), you'll need to convert a string to an array first, then back.

console.clear();
let str = "12345.00";
let strToArray = str.split("")
console.log(strToArray, "<= strToArray");
let spliceMethod = strToArray.splice(str.length-1, 1)
str = strToArray.join("")
console.log(str, "<= str is changed now");

Answered   2023-09-20 20:29:35

In cases where you want to remove something that is close to the end of a string (in case of variable sized strings) you can combine slice() and substr().

I had a string with markup, dynamically built, with a list of anchor tags separated by comma. The string was something like:

var str = "<a>text 1,</a><a>text 2,</a><a>text 2.3,</a><a>text abc,</a>";

To remove the last comma I did the following:

str = str.slice(0, -5) + str.substr(-4);

Answered   2023-09-20 20:29:35

You can, in fact, remove the last arr.length - 2 items of an array using arr.length = 2, which if the array length was 5, would remove the last 3 items.

Sadly, this does not work for strings, but we can use split() to split the string, and then join() to join the string after we've made any modifications.

var str = 'string'

String.prototype.removeLast = function(n) {
  var string = this.split('')
  string.length = string.length - n

  return string.join('')
}

console.log(str.removeLast(3))

Answered   2023-09-20 20:29:35

Try to use toFixed

const str = "12345.00";
return (+str).toFixed(1);

Answered   2023-09-20 20:29:35

Try this:

<script>
    var x="foo_foo_foo_bar";
    for (var i=0; i<=x.length; i++) {
        if (x[i]=="_" && x[i+1]=="b") {
            break;
        }
        else {
            document.write(x[i]);
        }
    }
</script>

You can also try the live working example on http://jsfiddle.net/informativejavascript/F7WTn/87/.

Answered   2023-09-20 20:29:35

  • Thanks kamal. However, I've marked the answer above as accepted for my needs. Notice the green check mark above. Though, I did check your code. :) Now, in my situation, I only know the common end character sequence. It would be better to just start checking from the end of the string. Your suggestion would fail if I have a string that looks like "foo_b_bar", and I only want to take out the last "_bar". Thanks though! It's quite an interesting experience to ask a question over 2 years ago, and still receive answers for it today. :) - anyone

@Jason S:

You can use slice! You just have to make sure you know how to use it. Positive #s are relative to the beginning, negative numbers are relative to the end.

js>"12345.00".slice(0,-1) 12345.0

Sorry for my graphomany but post was tagged 'jquery' earlier. So, you can't use slice() inside jQuery because slice() is jQuery method for operations with DOM elements, not substrings ... In other words answer @Jon Erickson suggest really perfect solution.

However, your method will works out of jQuery function, inside simple Javascript. Need to say due to last discussion in comments, that jQuery is very much more often renewable extension of JS than his own parent most known ECMAScript.

Here also exist two methods:

as our:

string.substring(from,to) as plus if 'to' index nulled returns the rest of string. so: string.substring(from) positive or negative ...

and some other - substr() - which provide range of substring and 'length' can be positive only: string.substr(start,length)

Also some maintainers suggest that last method string.substr(start,length) do not works or work with error for MSIE.

Answered   2023-09-20 20:29:35

  • What do you mean? String.prototype.slice is a native method - anyone
  • it only what you said. Javascript native method, but also jQuery slice() method for DOM manipulation: jQuery API: .slice(). AND SURE, that is CAN BE FIGURED like a polymorphic inheritance of JS Array.slice(), but it is two different methods, and I think needs to tell it apart. So it's just an approximation to this knowledge. - anyone
  • If you call .slice on a variable that is a string, it's going to do just what the OP wanted. It doesn't matter if it's "inside jQuery" and there is no way it could "interfere" in any way unless you overwrite String.prototype with jQuery, which I am sure will prevent ANY javascript code from working. Your answer just says that other answer is not good and the argument you provide is incorrect. - anyone
  • I can agree with @naugtur this answer is wrong, the string's slice method is not effected by jQuery. - anyone
  • I think the point naugtur was making was just that, feasibly, you could end up with a string wrapped by a jQuery object (e.g. if you do some fancy .data manipulation and end up with this "string"), which if you called slice on it, would not do what you want. That said, this isn't really a helpful answer. - anyone

Use substring to get everything to the left of _bar. But first you have to get the instr of _bar in the string:

str.substring(3, 7);

3 is that start and 7 is the length.

Answered   2023-09-20 20:29:35

  • this only works on "foo_bar" not on "foo_foo_bar", the question was about a string with any length but a known end. - anyone