JavaScript chop/slice/trim off last character in string

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?

Answers:

Answer

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);

Answer

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));

Answer

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.

Answer

A regular expression is what you are looking for:

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

Answer

How about:

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

Answer

Use regex:

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

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

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

  1. ., matches last character, in this case

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

  1. $, matches the end of the string

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

Answer

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.

Answer
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
Answer

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

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

The shortest way:

str.slice(0, -1); 
Answer

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);
Answer

@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.

Answer

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.

Answer

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);

Answer

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
Answer

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, "");
Answer

Try this:

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

Answer

const str = "test!";
console.log(str.slice(0, -1));

Answer

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/.

Answer

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

Answer

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.

const string = "?????";

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

const utf16Chars = string.split("");

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

In addition, the RegExp answers don’t match line breaks at the end in their current form:

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 = "?????";

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

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.

Examples:

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

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

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

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

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

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